It took a lot of researching and tinkering but I got Sonic Heroes PC working on Windows 10, with 4K and Widescreen.
I can't really do anything about the UI right now but this is good enough for now. I might lower the FOV a bit if I can since it might be a little too high.
I'm still not even done tinkering as I need to do some hex editing to fix a few issues, mostly to do with transparency effects in some places. But the majority of the work is done.
Even getting the game to simply boot required me to replace my .exe with a patched one, as this game and a lot of old games use a DRM system that, long story short, Microsoft has stopped supporting due to it potentially being a security risk in modern computers. So you need to make these games ignore the DRM check entirely.
Most people resort to a virtual machine or a cracked, pirated version of the game, but I'm happy to not have to fiddle around with that.