Can someone link me any kind of guide on alchemy? After 35 hours I still don't understand fully how exactly it works so any hints, especially regarding stuff like new archetypes, would be appreciated
Only the dev knows "exactly" how it works. But the TL;DR of alchemy is that components transmit energy and this energy gets amplified, reduced or reversed according to the materials involved. A combination of certain materials in certain order with certain energy values can create a alchemical art, and some of those can do transmutations. Some doll object data can only be obtained via transmutation and when extracted they will give you one of three items. Every other object data has a single item, but it's extremely rare to obtain it.
The amount of energy will influence the amount of synch + stat gain, and your chances of obtaining resistance/null traits.
Archetypes have special rules. I do not know how it all works.
There are special archetypes that override everything, and these are guaranteed to trigger on a synch if you met their condition. The most basic example being entropy archetype (which is frequently warned, remember?). There are sister archetypes if you met their conditions, like if you have enough str and end, and you synch, you have a chance to obtain lolita knight archetype if you didn't and you have less than 2 base types.
Evolution types have both special types, and non-guaranteed types, and the game does offer some hints towards some of them, but never nothing specific. "High INT" or "high END". I have only managed to obtain one of the advanced archetypes after 2 endings so... 🤷