I regularly transition from Thinkpad/laptop and 60-75% standard boards to a 60% split Ultimate Hacking Keyboard, 40% ortholinear planck, and split planck (Let's Split). The only thing that ever messed me up was using split spacebars, where one thumb maps to something besides space. I end up being confused when my less dominant thumb doesn't activate the keypress on a regular spacebar. :\ Hard to overcome the muscle memory, so I've sworn off of split spacebars unless I change all my boards to split space. Which is impossible for laptops.

Aside from that, transitioning takes no more than half a minute for it to feel natural again.