there is no use of super power mcu if the mechanic cannot handle the speed. once i speeded up my knock off prusa (the china master copy from where i learnt to build another machines at fraction of cost), but the result is poor print mainly due to mechanical reason iirc, so i slow it down. the atmega mcu has more time waiting than compute, i dont see any fault or jittery motion even on fast speed setting that can be narrowed down to mcu bottlenecking, i got a good GUI respond as well, no pause in motion. imho, faster mcu is mostly gimmick on better colorful GUI etc, but i maybe wrong, anyway my prusa works fine in term of mcu processing. the driver stucked in female header is not a good excuse to dismiss OSHW reprap/marlin/ramps as the header is meant to put the right driver on (extendible and configurable) if user see not enough current or missed steps, user should upgrade to bigger version motor driver and the motor, thats the idea instead of buying another new machine that costs another 3-10X. imho as a person who built some proto machines from scratches. i believe we can buy that cheap arduino + ramps shield board and then put another appropriate driver, motor and gearing system to lift a tanker.
the earlier proto-bethan i showed is pretty much a standard OSHW reprap 3d printer build (arduino mega + populated ramps shield, except with different mechanism of and the short Z height and head assembly from 3d printed parts), no need to fiddle with marlin FW, just copy to mcu as is, use FlatCAM OSS to translate gerber to gcode and good to go. i only need to hack GCode for manual drilling process, ie the head will go to drill position (translated from NC Drill file), and then i will correct pcb position and hit enter (encoder button) and head will start drilling. alot better than looking at PC screen to find which hole position and then drill with freehand. 0.5 - 0.8mm drill bit and freehand dont work together nicely, i killed many bits before, before even successfully punching a hole.
there is one word for faster mcu (even OSHW version), its "ex pensive". and close feedback loop motor system? few words... more more expensive than the expensive. a single stepper motor system including the close loop control board can cost few times than my prusa. let alone building complete system using 3 or 4 of that. imho CNC machine only suitable if people want to get serious in substrative CAM such as making mould, aluminium rf shield and enclosure or a some quality metallic pendant for SWMBO etc, but for scratching pcb? i dont think so. anyway a sure way to get a really working machine is go to Hitachi or Toyota factory and ask what CNC they use, buy that.