LR3 is real good for this. @DougJoseph has done it and Ryan has one, I believe there is one more but I cant remember who.
Extremely well documented, worth a read if you are interested in building one
Water cooled adds a lot of weight and complexity to it. I run a vevor air cooled spindle in both of my LR3s and it is much quieter than a palm router. And it fits right in the Makita mount already designed by Ryan. I remixed his mount to give some more surface area to grab and be able to slide the spindle up a little higher and it works well. Located here on Printables. I printed mine out of ASA because the spindle can get quite warm. But I have run one printed in PLA without issue. I will say you still have those times where the bit cutting through the wood makes a ton of noise as well.
I have run my NEJE A40640 on my LR3 off of @DougJoseph Kinematic mount and it worked quite well. Not sure if it would hold a 20w or not, mine is only 10w. I have a 20w on my primo and its quite a bit larger so YMMV