When it comes to the Banebots wheels dont bother with the green ones, you will be burning a set every fight. Orange is ok but be prepared with spares as you will need them. I would stick with blue TBH. They are more than grippy enough and will last you an entire event. I did testing with Conker 3 on concrete for a good hour and ran the whole 2014 champs on the same set of wheels with no issues.

As for the size... the drills at full speed on 124mm wheels will be very quick, possibly too quick and with an unsupported shaft probably wont last that long either due to a bent shaft or trashing the internal gears.

Go with EC5's for your connectors as you are building a spinner. The current spikes and general high ampages will burn out Deans and TX60's. And even if they don't its better to be safe than sorry.