4R100 controllers, 4x4 to 2WD conversion?

Been a few decades since i messed with cars, but am considering building something.

Drivetrain is a 2001 ford 5.4 and 4R100 (rebuilt) 4x4 setup out of an expedition.

From what I understand the GEM controller runs 'the body' and trans, etc. So I'll need an aftermarket controller - not for drag racing or anything exotic, just basic street use. I've seen some for $250 and others pushing $800.

Any recommendations?

Also, not sure I want a 4x4 and back in the day you could swap tailshafts and housings for 2x4 and 4x4 use. Is this still true on a 4R100?

I've used PCS controllers and they are expensive, but very nice! I've heard the optishift ones work pretty good too.