Choosing your reflectors depends on how high you need to mount your radions.
I use a lumenbright large over 36x36 @ 16" from bottom of reflector to water line. t's enough coverage but you will get a /-\ type of coverage that is pretty apparent unless you mount it higher. With this reflector it's really hard to fit anymore supplement lighting besides maybe 2 t5s in the front and back.
For your setup, I'd recommend finding someone with the old Lumenmax 2 reflectors. They are small in footprint and provide fairly good coverage when mounted lower.
400w all the way for color/growth but you're supplementing with 3 radions so maybe 250w may be a better fit.
For ballast - From blueuest to whitest IME.
Hamilton - Icecap - Lumatek - Galaxy. I've use the galaxy selectable at the highest setting for my 400w setup, it's given me the best growth and color.