How freely do your wheels spin

wheels should spin free without the caliper on, don't mistaken a bent rotor or sticking pistons on the caliper for worn bearings.

NSK or FAG is who I always go with. NSK is the oem bearing for most everything on a JAP bike.

If you are feeling baller you could go for some Ceramics from worldwidebearing.com

SKF Explorer bearings are pretty much the best bearing you can buy, expensive but they really are the best. Not as smooth and frictionless as a ceramic bearing but they can take so much more load and have a much longer service life, especially in a 2RS (rubber seal) designation which suits wheel bearings.

My wheels spin very freely, especially on the front, the rear not so much as I have an O-ring chain on at the moment but when I had a standard race chain on it was just as good as the front. I could use my pressure washer to spin both wheels at a pretty fast rate.

Get 2rs bearings, abec5 minimum. Take the dust shields off and remove the thick grease they come standard with and clean them out. Add several drops of royal purple synthetic trans fluid to them and put the dust sheilds back on. Super smooth, spin for days and will last a lot longer than a bearing with grease packing.

How do they spin with the chain off and the brake pads separated from the disc?

I remember having a problem with my front wheel being hard to spin and it ended up being a grody brake caliper. Rebuilt it and it spun much more freely.

My rear wheel takes a bit of force to spin, I attribute that mostley to the o-ring chain

When I can't spin my rear wheel with the power washer I know it's time for a light sanding on the axle and some grease in the bearings

How does sanding the axle help the wheel roll?

When I was 16 I used to go camping in the Cascade mountains with some old fockers. We rode all day ...trails, hill climbs, and logging roads. The more senior riders knew of some vicious log slides for hill climbs and down hills. Learned a lot of skills riding with those guys!
Every ride there was a coasting contest to determine who did the best maintenance. At some point we stopped and took of our chains. We lined up and pushed off...... lots of fun - let me tell you my bearings were greased and ready....