@brampie there is a limit in the firmware for what the extruder current can be which i believe is set to 1A at the moment but I know they tested up to 1.6A.
The 2240 used on the roto board reports its temperature so you can use that to monitor if the board is too hot.
Depends what current you want to run your extruder at.
Yes you get an XT30+2 cable
And yes, theres the Fly-RRF36, Fly SB2040 Max V3 and Fly-SB2040 Pro Max V3 made by Mellow