Мне нравятся духи, которые не пахнут слишком сильно, а брови я обычно вообще не крашу.

Russian often uses нравиться to mean to be pleasing / to appeal to someone.

So:

• Мне нравятся духи literally means Perfumes are pleasing to me
• мне = to me (dative case)
• нравятся agrees with the thing being liked, not with the person

You could say я люблю духи, but that usually sounds stronger, more like I love perfume.
Мне нравятся духи is often a more natural way to say I like perfumes.

Because the subject is духи, and духи is grammatically plural.

With нравиться, the thing liked is the grammatical subject:

• Мне нравится книга = I like the book
• Мне нравятся книги = I like books

Here:

• духи = perfume / perfumes
• therefore: нравятся

Yes, but in Russian духи is a plural-only noun when it means perfume.

So Russian says literally something like perfumes, even when English often uses singular perfume.

Examples:

• Эти духи дорогие. = This perfume is expensive.
• Мне нравятся эти духи. = I like this perfume.

So the plural verb here is completely normal.

Которые means which / that and introduces a relative clause.

In:

• духи, которые не пахнут слишком сильно

it means:

• perfumes that do not smell too strong

It agrees with духи:

• plural
• nominative

It is nominative because которые is the subject of не пахнут.

Again, because the subject is plural:

• духи пахнут = perfumes smell
• духи не пахнут = perfumes do not smell

If the noun were singular, you would use пахнет:

• духи → пахнут
• аромат → пахнет

It means too strongly or too intensely.

• слишком = too
• сильно = strongly

So:

• не пахнут слишком сильно = don’t smell too strong / aren’t too strongly scented

A more natural English translation is often that aren’t too strong.

А often marks a contrast or a switch of topic.

Here the sentence moves from one topic to another:

• I like perfumes...
• but/as for eyebrows, I usually don’t dye them at all

So а works well because it sets up a contrast between the two parts.

Very roughly:

• и = and
• но = but
• а = and/but/as for..., with contrast or topic shift

In this sentence, а is the most natural choice.

Russian word order is flexible, and moving брови to the front gives it extra emphasis or sets it up as the topic.

So:

• я обычно вообще не крашу брови = neutral
• брови я обычно вообще не крашу = as for eyebrows, I usually don’t dye them at all

This fronting makes the second half sound more contrastive, which fits well after а.

It is accusative plural, because it is the direct object of крашу.

The dictionary form is:

• бровь = eyebrow

Plural:

• nominative plural: брови
• accusative plural: брови

Because бровь is inanimate, the accusative plural looks the same as the nominative plural.

So in this sentence, брови is accusative even though it looks identical to nominative.

Because the sentence describes a habitual action:

• обычно = usually

For repeated or habitual actions, Russian normally uses the imperfective verb:

• красить → крашу

Покрасить is perfective and would usually refer to a completed single action:

• Я покрашу брови. = I’ll dye my eyebrows.
• Я обычно не крашу брови. = I usually don’t dye my eyebrows.

So крашу is exactly what you want here.

Here вообще adds the sense of at all or really / basically.

So:

• я обычно вообще не крашу means something like
• I usually don’t dye them at all

It strengthens the negation.

Depending on context, вообще can mean different things, such as:

• generally
• overall
• at all

Here, at all is the best fit.

Because in Russian, with body parts, the possessive is often omitted when it is obvious from context.

So Russian often says:

• Я мыл руки. = I washed my hands.
• Он закрыл глаза. = He closed his eyes.

Likewise:

• брови я обычно вообще не крашу naturally means I usually don’t dye my eyebrows at all

You could say свои брови, but it is usually unnecessary unless you need emphasis or contrast.

It can cover both ideas depending on context: to color / tint / paint eyebrows.

In everyday speech, красить брови may refer to:

• applying eyebrow makeup
• tinting/dyeing them
• coloring them in general

The exact English translation depends on context. In this sentence, dye/fill in/put makeup on my eyebrows are all possible, but dye or do my eyebrows may sound most natural depending on the situation.

Yes. Духи can also mean spirits in some contexts, but here it clearly means perfume.

Russian often has words whose meaning depends heavily on context. In this sentence, because of:

• нравятся духи
• не пахнут слишком сильно

the meaning perfumes is unmistakable.

Both are possible, but they place the focus slightly differently.

• не пахнут слишком сильно = a straightforward way to say don’t smell too strong
• не слишком сильно пахнут = also natural, with the not too strongly idea grouped a bit more tightly

Russian allows this kind of variation fairly freely. The version in your sentence sounds completely natural.