For new construction, should the plumbing for spigut, faucet handle, and shower head be installed before placing the tub/shower stall in place or after? Or doesn't it matter?

Thanks

Since you failed to inform me if this installation will be a manufactured tub/shower stall or a custom built tile one,
I'm going to assume that it's a manufactured unit made of plastic or fiberglass.
The water and drainage will be roughed in first and unless the holes for the tub spout, valve and shower head  are already in place you will cut and drill the openings to match the rough in.  The unit can then be set in place and secured.  Next you will install the trim, spout, valve, shower arm and head and drain  and stopper assembly.  You will need a 14"X14" access hole cut in the wall behind the unit at the base behind the drain  to install the drain and tub shoe and overflow/ stopper assembly and connect it to the trap.  More questions?  I'm as close as a click.  Good luck,  Tom

Thanks for your timely response. Your assumption was correct.