Rear wheel, how much lateral movement is normal?

Normally when you lean hard that you might effect the rim flexing to the opposite way to the lean you're rarely pedalling at the same time, certainly you're unlikely to be able to pedal hard and have a significant lean and your bodyweight is going to have more of an impact on rim movement than your output from your legs.

Don't know what your rim is but it sounds like it may not be suitable for you in terms of spoke count and as alluded to above spoke tension/build may not be correct either.

Another thought is have you had any impacts on the bike, is the rear triangle straight/aligned correctly, clutching at straws but can't think of anything else.

My guess from what you've described:

1. Wider rim as @nniff says. Slacken off the brakes before you go retensioning the spokes and cracking the rims.

2. Softer wheels, i.e. with more lateral flex, no bad thing, they can be more comfortable for long rides than super stiff racing wheels.

3. If there is movement in the hubs, you should be able to move the axle laterally with the wheel off the bike. If they're quality hubs there should be bearing pre-load available, usually a threaded section on the non-drive side with a pinch bolt.

4. You're just pumping out amazing huge watts and showing off about the rims hitting the brake blocks ;-))))

Problem is you haven't said how much movement with how much force. To me it sounds like the spokes need tensioning (they can all be slightly too slack, the wheel will be round and true, but you will get too much movement). The LBS should be able to tell you if the spokes are properly tensioned (they should have a tension gauge). If you can't feel play in the bearings you then there is nothing to do with the bearings to fix it, unless you have a 2 part back axle (some back axles have 2 parts which screw into each other and can come undone). 

Some movement is normal, moderate pressure with your thumbs will be enough to push on to the brakes.

It may be that the rims are wider than your last ones and so slackening the brakes off may be entirely appropriate.  Clearly, I can't see them, or know how much you have backed them off already but, for consideration...

my first thought would be a worn cartridge bearing but obviously not....assume rim brakes so rim is flexing? have some spokes slackened off? is the spoke count appropriate to operator size? 

Are you good with a wrench? If yes, here is the Novatec 172 hub schematic. Do a hub maintenance and check for damaged parts. Unfortunately I was not able find descritpions to part numbers, but you should be able to get those from Novatec.

Sounds a bit extreme if you're feeling it through the corners. I have a pair of Campagnolo Scirocco 35s and there is very noticeable movement when I app!y pressure to the side of the rim, but strangely I don't seem to feel it when actually moving. They've always been like it straight out of the box.