A bent axle probably wouldn't cause wheel wobble, the wheel would be offset and spin true. The most common & simple causes to look for are a pinched inner tube (between the wheel halves) or improperly seated tire. Either could result in a wheel wobble that wasn't there before the tire change. Obviously, a bent wheel or hub could be the culprit.
Brake shoes are one item where it pays to buy the best. They don't cost all that much, so why take chances...go with OEM Honda or quality aftermarket such as Kitaco or Ferodo. The Z50, CT70, CT90/110 all use the same brake shoes and the bigger bikes were good for 55-ish top speeds. I don't trust the drum brakes beyond 55mph, period. That doesn't mean that they won't cut it for certain, but the feel doesn't inspire a lot of confidence and they weren't designed for that speed. Before converting to a front disc brake, I always used compression braking to slow the bike down to 50 before applying the brakes.
This is only my take on things, others may beg to differ. That said, there's no substitute for a properly setup disc brake. I run OEM Honda/Nissin 220mm discs with the twin piston calipers and the difference is night & day. You don't have to cruise at 65mph to realize the improvement in stopping power. At that speed, I wouldn't expect the drums to work very well at all. Below 60, though, is some gray area, especially for a skillful rider. A couple of recent events really opened my eyes. I rode a K0 fitted with a Nice 110 and stock brakes/suspension. After three years of riding a similarly powered bike with upgraded suspension & front disc, this was an exercise in near-terror...at least initially. After a few miles, I did begin to adjust my riding style but somehow just never felt completely comfortable. Getting back on my own bike afterward, I nearly did a stoppie the first couple of times the brakes were applied. The other, more serious incident, came when I was riding along, with my wife aboard and some $#@*&^!!! ran a red light directly in front of me while traveling along somewhere between 50-55mph. I really appreciated having "overkill" braking power at that moment. Even with the rear wheel getting light enough to induce partial lockup, there was just barely enough room to stop in time. I doubt that the stock drums could have equalled the stopping distance. An extreme example, to be sure. But on the road, anything can happen. With 124cc moving you along, you're into "real bike" territory (I consider 55mph+ "real bike" speeds) and real bikes should have real brakes. In this state, anyway, 125cc is enough displacement to legally ride on freeways. You aren't required to have a death wish to ride a CT on a freeway...but it helps. Likewise for 65mph sprints with questionable braking power for that speed. You can probably get away with it for a long time. IMO, a bike should be balanced with brakes & suspension to match engine power, to be reasonably safe. Then again, that's just my opinion...I could be wrong.
as far as the high tech front end,it wouldnt hurt.
