Threw on Doom 64 EX last night and played through a couple of levels ().I have an original cart I can photograph if mods need evidence? I guess it's technically against the TOS...
Doom 64 with mouselook is really, really easy. Like, there is no threat whatsoever easy. Need to restart on a higher difficulty - I think my old save is on Hurt Me Plenty.
That's a common issue with a lot of N64 focused shooters I've played on PC. I remember Turok 1/2 being hard as balls, but playing the PC versions with a mouse was a walk in the park.
Also Doom 64 EX has built in 360 controller support, so that could help.