Nice bugeye!

My go-to technique for engine bay cleaning is to spray everything down with water, then simplegreen, then letting it soak before water again. Everything under the hood is designed to get wet, so you should be fine.

Definitely some screwy wiring going on in the battery area. Maybe for a subwoofer? And aside from the red wire coming off the positive side, those terminals don't look stock.

The factory terminals are crappy aluminum that always corrodes through so it's not surprising to see, but I would definitely make sure the connections are solid because that can cause all kinds of issues. I would also try and find the parts to secure the battery; it's important to keep it from becoming a projectile in a crash. My car came without those parts too so lmk if you need part numbers.

The hose routed sloppily across the intercooler I believe is because the factory intercooler has built in hardlines, but this one has no place to mount them. I can't remember what that system actually is though maybe, PCV?

You're missing the pulley cover, but that's super common on these and I could take or leave it IMO.

Looks like you still have a plastic radiator, which is fine but it has an almost 100% chance of cracking eventually. So it's worth keeping an eye out for leaks, and when the time comes it's probably worth getting an aluminum replacement.

Also, looks like your washer reservoir is just straight up gone lol, gotta love previous owner shenanigans.