increased rigidity and weight - will help increase print speed.
Nema 24 for moving things around should be fine.
wouldn't use it for the extruder though, unless you're planning on a bowden setup (why would you ????).
Although for actual print speed the classic I3 design is a lot faster than standard cartesian box setup. That's pretty much the slowest setup.

I've got a rep pro clone, i3 clone and a delta. Speed wise the delta is the fastest, the i3 is pretty close behind and the rep clone runs at about half the speed of the others - flat out.

Get it right with a delta and they'll blow everything else away for speed and qualiy.
A good I3 (NOT ender range) will also print at speed with excellent quality.

Good i3; dua bed side rails, direct drive extruder and dual z screw - basically as Josef prusa designed it. Not as it has bee crippled by cheap chinese manufacturers like creality.

With linear rails for side supports and the nema 24's with 10mm belts an a super rigid frame you could really rack up the speed.