Hey there. I was one of the people that worked on the english patch, and I had to dig quite a bit on the graphics system.
Joyoland made quite a lot of questionable decisions, to say the least. All those options in the ini file are useless, probably a leftover from the Kiseki games. The game ignores them. Same goes for the shaders, a lot of the game logic needed for the effects is still in the game, but the actual shaders are gone, being replaced with really basic ones. Also, they didn't bother to enable 60 fps. We were able to get it almost right for most of the game (menus will keep going at double speed, but I think it's worth it) having no source code, so, there is no reason they could have not made a better job.
Also, the original chinese version runs at 16 bit colour depth, you can see a lot of color banding in some places (like lights). I fixed that for the patch.
About the shadows, are there any shadows on the game, besides the little circle below the characters?
I'm working on restoring them (I've been busy with this for a few months, it's quite tricky to get it right without glitches, the shadows had problems even in theVita version).
If I ever get rid of the glitches (I'm going to end up rewriting a lot of the rendering system, and even editing the 3D model data if it keeps going like this), I can make them look a lot better than what the Vita game has,as long as your PC can handle the higher resolution shadow texture.
As for the textures,they are the same as in the Vita version (most of the data files are identical), and when they are different, they've got better quality. I think they look worse because there is no mipmapping in the PC build.
I've been working on a Gedosato plugin that tried to fix this, but it's really unstable, so I guess I'll try another way.