how is this going' to work ? guitar freaks without a guitar ? and a fishing game without a reel ?
Probably as well as playing pacman with an 8-way: ie people who played it in the arcades/console will complain how bad non-original controls are, while those who never played the game with the original hardware will be mixed, some even doing quite well with what ever they are using.
Guitar freaks: looks like mame is using seven buttons: P1 Effect 1, P1 Effect 2, P1 Pick, P1 Wailing, P1 Button R, P1 Button G, P1 Button B
Bass: looks like mame is using the Y axis of the mouse; yes, not "dial", not "trackball", but "mouse".
Marlin: in addition to the bass mouse Y axis, marlin adds the X & Y axes of an analog joystick.
Never played any of the above, so I don't have an opinion of how well different setups will feel compared to the original controls. I'd
guess the ps2 guitar will work great with the
correct adapter once mapped correctly.