Gee, I hope it doesn't break a sweat, that would be horrible!!
Seriously though, I'm glad you figured some things out and I'm glad that it has such amazing quality after only a few days of tweaking it. This is all new ground and uncharted territory, but the preliminary results look great!!
So, were you saying the Z screw alignment could impact quality - or would you say that is not related, just visible and that is it? I would think that the Makerslide Z rails would and eccentrics on the wheels would dictate Z alignment. Also, I was thinking are there 3 eccentrics for each carriage? On the Z, couldn't some weird combination of eccentric spacers cause the carriage to be uneven from the bed? Also each Z motor likely has to be in the exact same spot, right? Can you just align those with the carriage laying on the bed flat?
Are you using like a .5 or .4mm nozzle right now?