The Nomad series can handle many-flute endmills just fine. I ran them on my 883 Pro before upgrading to a more powerful spindle.
However I’d only go as high as two flutes with <6mm tooling. More flutes with tools that small is an absolute pain in the ass in terms of chip clearing but the bigger tools have larger flutes so handle it better, so long as you’re still not taking crazy cuts.
If you’re going for >2 flute endmills, I’d definitely look at improving your chip clearing though. I’ve clogged 6mm endmills due to forgetting to turn my compressor on. If you’re doing open cuts it might be fine to do without but if you’re slotting, no way.
You’re the second person to bring this up and I don’t know where the idea comes from; it’s definitely not true on the 883 Pro. On the 883 Pro, you usually reach the limits of machine rigidity long before you reach the spindle torque/power limits and increasing flute count allows you to increase utilised spindle power/torque/MRR without increasing the cutting forces, so it’s a great way to get better MRR.
My guess is that this idea comes from people who don’t actually own Nomads or haven’t tried to push them to their limits.
A dust boot and vacuum is good at cleaning up mess and avoiding chip recutting as chips pile up but I wouldn’t expect it to do a whole lot in terms of chip evacuation. For that I’d add a compressed air nozzle.