difficult to answer without spoiling.
well, it is not a redo and not a continuation. instead it is ... everything is altogether different, and yet the same. and it is ridiculously complex vast. I still can hardly believe that that old version of rpgm does not outright explode in face of that scope.
Story and atmosphere are overall oppressive, even though shockful of humour, sillyness etc.
There is a lot LOT of hidden flavour content for characters which is always nicely in-character, it always adds.
some characters had a graphics redo, usually for the better for me. Eg. the succubi - more sexy, more hilarious, more likeable, even adorable/ moe (and early in). There are more playable and sexable characters, and you can have sex outside of battles.
Main problem to me is the difficulty level. "normal" is much too easy, early in you typically would get out of battles better than you went in. "paradox" (highest difficulty) is stupid, it actually removes from the game, still did it but was not fun. "very hard" or "hell" (iirc.) are okay-ish for normal fights, but for boss fights maybe too hard (Four Heavenly Bandits are the first very big hurdle).
I am not sure, but on normal, hard, very hard it might be possible to play without having to understand all its details.
disclaimer - I still have not played part 2 + 3. I wait until winter/ darkness come, because so time-consuming. And I have not yet decided if I want to go into part2 with the strongest build or with the silly build.
Also I am afraid if it will become too complex to be enjoyable for me*, that would be sad for me to experience. Eg. at end of part 1 there is a tower where you can continue to play-for-playsake, and it gets into that direction ... not for me.
*like the one-off battle against the holy berserker. one-off is fine, but always like that ... nah