if you get the xc-w you will find it really friendly to a new rider getting used to starting and stopping. the w stands for it's transmission having a wide ratio set of gears. the lower first gear makes it easier to pull away from a standstill at lower rpms. that same reason I mentioned gearing the yz down if cheap and convenient for you. the ktm xc has a heavier flywheel rotor than a motocross bike of the same size and make. flywheel weights are affordable for the yz of course. if you spent an afternoon on something like an xr200-400, drz 250-400, tt 230-250, yamaha wr of any size, honda crfx (250 or 450), Kdx 200 etc your transition to the yz would be a little easier, but I think you will get up to riding speed fairly soon.
Make sure your bike is tuned for slow speeds, especially make sure the float level is right. This is really important on used bikes, two strokes doubly so. Consider a hotter spark plug for your initial learning on the two stroke, just don't go for long high speed runs with it or under a hard load.
I tell people to get used to paddling the bike around with their feet (engine off). if you do that and get used to a gentle push off with your foot or feet on soft ground or uphill it makes it easier to get moving without stalling. stop on level ground or slightly downhill. makes it easier for restarts. understand that you will kill the bike quite a few times when you start out learning. dont get frustrated, dont let others rush you. dont let too many people talk to you at the same time. watch someone else do it, then start your own bike and try it, then try it again, and again. as soon as you can find a wide open flat spot, start your training. DO NOT DO IT in a closed in area or small place where there isnt enough room to do some gear shifting before easy slow turns are possible.
As soon as someone uses a phrase like "you will jerk your arms out of their sockets" or "put it in second so you dont jerk your arms out of their sockets (to start off)" or "put a larger countershaft sprocket on it, or a smaller rear wheel sprocket on it" etc, quit listening to them. better yet get out of ear shot.