Here is some reading material (I asked the same questions some years ago, so I'd thought I'd provide a bit more info):
Roland MT-32 and compatibles: https://en.wikipedia.org/wiki/Roland_MT-32
Roland Sound Canvas (in general): https://en.wikipedia.org/wiki/Roland_Sound_Canvas
The SC-55: https://en.wikipedia.org/wiki/Roland_SC-55 (answers your first question)
Just some additional points to consider:
- Just check when your particular game was released.
As a general rule, most games released up to early 1992 were written on the MT-32 or CM-32L (some games released before 1992 and that originally supported the MT-32, had General MIDI drivers released for them afterwards).
Bottom line, no General MIDI device (of which the Sound Canvas is one) can faithfully reproduce the sounds of an MT-32 (or one of its compatibles), especially where the game sends system exclusive messages to make use of custom sounds.
- For MT-32 based games, you need an MT-32 (or one of its compatibles). There were different revisions of the MT-32, but you can read up more about it here on Vogons or on the Wikipedia page.
For General MIDI compatible games, an SC-50, SC-55 or SC-88 will suffice (it all depends on what your budget is).
The SC-50 is just a cheaper version of the SC-55mkII (it has less features), but from a gaming perspective, there isn't any difference.
There were also different revisions of the SC-55 models (captial tone feedback, etc.), but there are already topics that covers this - Re: What module type, model and revision for GS/GM games?
If you're planning on playing your games on real hardware (i.e., not DOSBox), just take note that some MT-32 based games also requires an intelligent mode MPU-401 MIDI interface (https://en.wikipedia.org/wiki/MPU-401). However, there is a software based solution available (SoftMPU) that allows you to emulate an intelligent mode MPU-401 MIDI interface on most sound cards (that has an UART mode MPU-401 MIDI interface).
General MIDI compatible games do not require an intelligent mode MPU-401 MIDI interface and can therefore interface directly via your sound card's UART mode MPU-401 MIDI interface (using a standard MIDI cable).
Just be aware of the so called MIDI hanging note bug on most Sound Blaster 16 (including some SB32/AWE32) sound cards - refer http://www.vogonswiki.com/index.php/Hanging_note_bug.
Either get a sound card that hasn't got the bug, or use two sound cards (stay away from PCI based sound cards and stick to ISA based sound cards for better DOS game compatibility).