After problems with crosshair accuracy I decided to get the widescreen fix. Everything else works just fine. Except there is a problem with intro movie. Problem is, it only plays audio but doesn't show video. I found that source of the problem is d3d8.dll - after deleting that, intro movie displayed video again,
https://thirteenag.github.io/wfp#gtavc - it says that scripts folder (widescreen fix asi) can be used without d3d8.dll but this file seems to be essential because after I deleted it, the widescreen fix didn't have any effect.
It's not a big deal, I can just skip the intro movie and play game, but I like to watch the intro sequence and listen to the theme song every once in a while.