moo10123, yes, the BEC uses the voltage from your 12vdc battey(the one that came with your Stuart) and supplies voltage to your receiver!(very handy!....the Tamiya unit does exact same thing).
As for the "two stick control"......there are jumpers that allow you to set up type of control that you want....
• Left/Right independent (Tank) is what you are looking for....yes, it will do that
I use standard setup......right stick is throttle and stearing.
To control the turret , I use a Scorpion-mini for rotation.......all of this off of the 12vdc battery.The fan is "just in case",unit runs VERY cool .Sound is NOT proportional,nor do I have cannon or MG fire sounds with this setup.If I use original controler, I can make it happen...just not my priority.I also need to install a servo for gun elevation....maybe later.
I did same to my 1/9 Abrams
See attached pics