1. Not sure what "locking the bit rate in the Mia console" means. My soundcards in the past have had the option of using the soundcard's internal clock or relying on an external clock, i.e. the DAT playback machine. You want to do the latter, so the Mia doesn't resample an incoming 48k signal to its own 48k internal clock. Not sure what the setting is to do so on the Mia.
2. Looks like SAM 9 SE includes support for ASIO, and it sounds like the Mia has ASIO drivers, so go ahead and use them.
3a. The SAM configuration is pretty straightforward. Set up your recording / playback devices, define your TEMP directories, configure your recording virtual project's sample rate and bit-depth and you're ready to go.
3b. Note there are differences in the way SAM 9 SE perform SRC depending on the workflow you select.
A bit more here, though I originally found out about the issue on the
SAM forum. I haven't completed my testing of SRC in SAM 9 SE yet of performing SRC via Change Sample Rate v. Track Bouncing, but hope to have some samples up soon. FWIW, I'll also likely include the same master sample SRC'd through R8Brain. FWIW, on initial listening, I can't differentiate audibly between R8Brain and SAM at Ultra High 2, but like I said, I've not completed my testing yet. And just because I can't hear a difference, doesn't mean it doesn't exist and isn't audible to others.