The toilet and sink won't benefit from 3/4" pex, but the tub/shower will (at least filling the tub, if you only have one showerhead, it won't make much of any difference when showering). Depending on the type of pex you use, and the diameter, they each have different minimum bend radii, with type-A pex being the most flexible. The type reflects the manufacturing method (there are three types -A, -B, and -C, with -B and -C being less flexible). It also depends on the temperature of the pex when you try to bend it and whether you're going against how it was coiled in the roll or not. A bend support for one brand may be too sharp of a curve for a different brand's pex depending on the type.
Avoid extra fittings when possible. If the space within one stud bay requires it to be too tight of a bend, and you can run the supply in the next one over, you can usually avoid that sharp bend by using the whole bay next to it, then go straight into where you need it. Also, do NOT use pex AFTER the shower valve for the tub spout or you'll likely run into problems. Do that in copper or brass.