I’m late to the party sorry, but pretty much everything has been said.
I bought a G-Penny kit (story around that here, and about programming it here. Don’t be afraid by the pages of params, I just wanted to be super thorough, but in reality you’ll only have to tune a couple of parameters and off you go).
Runout on those chinese spindles is supposedly hit and miss, but either I got lucky or the runout is statistically small enough to not have to care about it. Mine was as advertised.
Water-cooled vs air-cooled: I would go water-cooled again, no doubt, but that is down to personal preference. The quietness is what I was after, but I found that water-cooled has a second interesting side effect: you can run the spindle arbitrarily slow, e.g. 100 RPM if you want to. Granted, there are not many situations that call for sub-5000 RPM, but it’s still useful to have this capability. With an air-cooled spindle you need to set a minimal RPM to ensure a proper cooling airflow. I also like the absence of downdraft from the spindle onto the piece.
Power: 2.2kW is definitely overkill, 800W appears to be nice and plenty enough for wood, and 1.5kW is probably the sweet spot that covers everything. On a regular Shapeoko3 I would have said go 800W, on a Pro with the extra rigidity I think 1.5kW makes sense.
I wish there was an option for a water-cooled spindle with a quick tool change mechanism like on @WillAdams’s Mafell
If you can afford a Mechatron, then that defnitely looks like a good choice to remove the randomness of the “shopping on Ali” experience.