Learn Hardcore Swedish: Jag tycker egentligen att hennes personliga stil är viktigare än vilket mode som är modernt. - I actually think that her personal style is more important than which fashion is trendy.

tycka (tycker, tyckte, tyckt)
Used for opinions, judgments, attitudes.
- Jag tycker att hennes stil är viktig. = I think (in my opinion) that her style is important.
tro (tror, trodde, trott)
Used for beliefs about facts, guesses, or faith.
- Jag tror att hon kommer sent. = I think / I believe she will be late.
- Jag tror på Gud. = I believe in God.
tänka (tänker, tänkte, tänkt)
Used for mental activity (“to think about something”) or plans/intentions.
- Jag tänker på henne. = I am thinking about her.
- Jag tänker köpa en ny jacka. = I’m planning to buy a new jacket.

In your sentence, we have an opinion about what is more important (style vs fashion), so tycker is the correct verb.

What does egentligen mean here, and where can it go in the sentence?

egentligen roughly means “actually”, “really”, “in fact”. It softens or nuances the statement, often implying:

a contrast to what people might expect, or
that this is your real or deeper opinion.

In your sentence:

Jag tycker egentligen att hennes personliga stil är viktigare …
= I actually / really think that her personal style is more important …

Common positions for egentligen in this kind of sentence:

Jag tycker egentligen att hennes personliga stil är viktigare …
(neutral position, modifying tycker / the whole opinion)
Jag tycker att hennes personliga stil egentligen är viktigare …
(slightly more focus on the style being “really” more important)
Egentligen tycker jag att hennes personliga stil är viktigare …
(fronts egentligen, adding a stronger “to be honest / actually” feeling)

All are grammatical; the difference is mostly in emphasis and nuance, not basic grammar.

Why do we need att after Jag tycker, and can it be left out?

Here att means “that” and introduces a subordinate clause (a “that-clause”):

Jag tycker att
- [hennes personliga stil är viktigare än …]
  = I think that her personal style is more important than …

About leaving it out:

In spoken, informal Swedish, many people drop att after common verbs like tycka, tro, säga:
- Jag tycker hennes stil är viktigare än … (informal speech)
In standard written Swedish, you normally keep att in sentences like this.

Also note the word order in the clause after att:

att hennes personliga stil är viktigare
Subject (hennes personliga stil) comes before the verb (är).
You do not invert the verb there (att är hennes stil viktigare is wrong) because Swedish subordinate clauses do not use V2 word order.

Why is it hennes personliga stil and not sin personliga stil?

Swedish has special reflexive possessive pronouns: sin, sitt, sina.
They are used when the possession belongs to the subject of the same clause.

sin – for en-words (en bok)
sitt – for ett-words (ett hus)
sina – for plurals (böcker, hus)

Example:

Hon gillar *sin stil. = She likes *her own style.
(subject and possessor are the same person)

In your sentence:

Jag tycker egentligen att hennes personliga stil är viktigare …

The subject of the main clause is jag.
Inside the subordinate clause (att hennes personliga stil är viktigare …), the subject is hennes personliga stil/stilen.
The “her” here refers to some other woman (not “jag”).

Because the possessor is not the subject of the clause she appears in, you must use hennes, not sin.

Using sin here (att sin personliga stil …) would be ungrammatical and confusing.

Why does the adjective become personliga and not just personlig?

Adjectives in Swedish change form depending on:

gender/number of the noun (en/ett/plural), and
whether the noun phrase is definite or has a possessive.

Basic pattern with personlig (“personal”):

Indefinite:
- en personlig stil
- ett personligt brev
- personliga vänner (plural)
Definite (with den/det/de or possessive like min, hennes):
- den personliga stilen
- det personliga brevet
- mina personliga vänner
- min personliga stil
- hennes personliga stil

After a possessive pronoun (min, din, hans, hennes, vår, er, deras) the adjective takes the definite/weak form, which ends in -a in the singular:

hennes personliga stil
min personliga bil
mitt personliga brev

So personliga is correct here because it comes after the possessive hennes.

How does viktigare work? Is this the normal way to form comparisons?

viktigare is the comparative form of the adjective viktig (“important”).

Regular pattern:

Positive: viktig (important)
Comparative: viktigare (more important)
Superlative: viktigast (most important)

Used like:

X är viktigare än Y = X is more important than Y
Det är viktigast = It is the most important.

This -are / -ast pattern is very common:

billig → billigare → billigast (cheap)
snabb → snabbare → snabbast (fast)
stor → större → störst (big) – irregular vowels but same idea.

You usually don’t say mer viktig in normal Swedish; viktigare is the natural form.

Why is the comparison word än used here, and when do we use än?

än corresponds to English “than” and is used after comparatives:

viktigare än = more important than
bättre än = better than
större än = bigger than

Your sentence:

… är viktigare än vilket mode som är modernt.
= … is more important than whatever fashion is modern.

Contrast with som, which is used with equality comparisons:

lika viktig som = as important as
Filmen var lika bra som boken. = The film was as good as the book.

So, after viktigare, än is the correct and standard choice.

What exactly is vilket in vilket mode, and why not vilken or vilka?

vilket is the neuter singular form of the question/relative word vilken (“which/what”).

Forms:

vilken – for en-words (common gender, singular)
- vilken bok (en bok)
vilket – for ett-words (neuter, singular)
- vilket hus (ett hus)
- vilket mode (ett mode)
vilka – for plural, any gender
- vilka böcker, vilka hus

Since mode is an ett-word (ett mode), you must use vilket:

✅ vilket mode
❌ vilken mode
❌ vilka mode (unless “modes” in plural, which is rare)

What is the role of som in vilket mode som är modernt?

Here, som is a relative/subordinating word roughly meaning “that / which”.

The structure is:

vilket mode – “which fashion” / “whatever fashion”
som är modernt – “that is modern”

Together:

vilket mode som är modernt
≈ “whichever fashion is modern” / “which fashion is modern”

So som introduces the relative clause (or clause-like unit) som är modernt, which gives more information about vilket mode.

Similar patterns:

Jag gillar den musik som hon spelar.
= I like the music that she plays.
Välj vilken färg som helst.
= Choose any colour (you like).

In this construction vilket … som …, you cannot just drop som; it’s needed to link the clause to the preceding vilket mode.

Why is it är modernt and not är modern?

The adjective in Swedish agrees with the gender/number of the noun it describes, even when it’s in predicative position (after är).

mode is an ett-word: ett mode
The neuter form of modern is modernt.

So:

Mode är modernt. = Fashion is modern.
Stil (en stil) is an en-word, so:
- Stil är modern. = Style is modern.

In your sentence:

… vilket mode som är modernt.

The adjective refers back to mode (ett-word), so it must be modernt, not modern.

Could you say something simpler like än modernt mode instead of än vilket mode som är modernt?

You can say:

… är viktigare än modernt mode.
= … is more important than modern fashion.

That is grammatical and understandable, but the meaning is a bit different:

än modernt mode
→ compares her style with “modern fashion” as a general concept.
än vilket mode som är modernt
→ more like “than whatever fashion happens to be modern”,
suggesting: no matter what is currently in fashion, her personal style is more important.

So the original phrasing with vilket … som adds a nuance of “any / whichever”, making it sound more general and a bit more emphatic.