Nowe kafelki są ładniejsze i łatwiej je czyścić.

Because nowe has to agree with kafelki in number and grammatical gender.

• kafelki is plural.
• It is not a masculine-personal plural noun (it refers to things, not male people).
• In Polish, adjectives with non-masculine-personal plurals usually take the ending -e.

So:

• nowy kafelek = a new tile
• nowe kafelki = new tiles

The form nowi is used with masculine-personal plural nouns, for example:

• nowi uczniowie = new male/mixed students

In this sentence, są is needed because it is the present-tense form of być (to be) and it links the subject to the adjective ładniejsze.

• Nowe kafelki są ładniejsze = The new tiles are prettier/nicer

Unlike some other Slavic languages, standard Polish normally does not omit być in present-tense sentences like this.

So:

• Kafelki są ładniejsze = correct
• Kafelki ładniejsze = incomplete in standard Polish, unless used very informally or as a fragment

Ładniejsze is the comparative form of ładny (pretty / nice).

The basic adjective is:

• ładny = nice, pretty

The comparative is:

• ładniejszy / ładniejsza / ładniejsze = nicer, prettier

Here it appears as ładniejsze because it agrees with kafelki, which is a non-masculine-personal plural noun.

So the pattern is:

• ładny kafelek = a nice tile
• ładniejsze kafelki = prettier tiles
• kafelki są ładniejsze = the tiles are prettier

Polish often forms comparatives with a special ending like this, instead of using a separate word like more.

Because łatwiej is an adverb, while łatwiejsze is an adjective.

That matters because here Polish is talking about the action czyścić (to clean), not directly describing the tiles with an adjective.

• łatwiej = more easily / easier
• łatwiejsze = easier (adjective form)

In English, easier can work in both kinds of sentences:

• The tiles are easier to clean
• It is easier to clean them

Polish usually separates these more clearly:

• łatwiej je czyścić = it is easier to clean them
• są łatwiejsze do czyszczenia = they are easier to clean

So in your sentence, łatwiej is correct because it goes with czyścić.

Je means them. It refers back to kafelki.

In łatwiej je czyścić, the verb czyścić needs an object: clean what?
Answer: je = them

So:

• czyścić = to clean
• czyścić je = to clean them

Without je, the sentence would sound incomplete unless you replaced it with the noun itself:

• łatwiej czyścić kafelki = it is easier to clean the tiles

Both are possible, but once kafelki has already been mentioned, using je is natural.

Because Polish often uses an impersonal construction with an adverb plus an infinitive:

• łatwo to zrobić = it is easy to do it
• trudno to zrozumieć = it is hard to understand it
• łatwiej je czyścić = it is easier to clean them

This is very common and natural in Polish.

So the second part of the sentence is not literally structured like the tiles clean more easily. Instead, it is more like:

• it is easier to clean them

That is why the infinitive czyścić appears.

Because short object pronouns like je often appear before the infinitive or verb in neutral Polish word order.

So:

• łatwiej je czyścić = the normal, natural order

You may also hear or see:

• łatwiej czyścić je

but that usually sounds less neutral and may give extra emphasis to je.

For a learner, the safest pattern is:

• łatwiej + object pronoun + infinitive

for example:

• łatwo go znaleźć = it is easy to find him/it
• trudno ich przekonać = it is hard to convince them

Yes. Both parts are about the new tiles, but they are expressed in two different grammatical ways.

1. Nowe kafelki są ładniejsze
   This is a normal subject + to be

   • adjective structure.

2. i łatwiej je czyścić
   This is an impersonal structure meaning and it is easier to clean them.

So English might package both ideas as parallel adjectives:

• The new tiles are prettier and easier to clean

But Polish often mixes these two structures naturally:

• są ładniejsze = are prettier
• łatwiej je czyścić = it is easier to clean them

That is completely normal Polish.

Yes. That is also correct, and it is very close in meaning.

Compare:

• Nowe kafelki są ładniejsze i łatwiej je czyścić.
• Nowe kafelki są ładniejsze i łatwiejsze do czyszczenia.

The difference is mainly in structure and style:

• łatwiej je czyścić focuses a bit more on the action of cleaning
• łatwiejsze do czyszczenia is a more directly adjectival description: easier to clean

Both are natural. The version with łatwiej je czyścić may sound a little more conversational and dynamic.