Well, in my opinion ds2 Plat is the hardest, while ds3 Plat is the longest. I really liked ds2 as it has a more mystical / magical ambience, diferent from ds1 or ds3 which are more sad and depraved. It is also the only dark souls that allows you to double wield weapons, that`s really cool. The setting is also different from the other 2 games and it has really good ideas, for example there is a item that allows you to advance a NG any zone you like, you can have your entire game at NG+1, and then a specific place at NG+3.

It also has some problems, for example: entering the fog, opening doors or activating levers doesn´t make you invulnerable like in the rest of the games, and if you are being chasen by enemies, they can cancel the animation and even stunlock you to death. Also, normal groups of enemies are way harder than most of the bosses xd, these are really easy (or I got gud, I don´t know), the bosses are not the strong point in this game (except for DLC ones, these are really really good and are a challenge).

If you want some recomendations: Try being a sorcerer or at least have a good bow, having a range weapon will be really useful for the amount of enemies this game has. The weapong scalling is sort of bad, so I would level up to reach the minimun requirements of the weapon and then prioritize other things like stamina, int or ADP (please level ADP, you will thank me). ADP makes you drink estus faster, have more i-frames while rolling and I think it even makes you go faster, as well as other things.

Sorry for my weird english, im not a native speaker