Mac keyboard user here. I considered this one a while ago, but the fact that it doesn't have an ESC key and also no function key row still holds me off.
So if you are switching keyboards all the time say from the UHK on your desktop to your laptop keyboard then your muscle memory is going to get a bit confused and keys aren't as easy to subconsciously hit. The mouse layer on the UHK is incredible and I find I try to use it all the time on other keyboards which obviously don't have it. Also function keys and escape haven't been as big a problem as I thought they would. Your brain just adapts quickly. One thing is that I do have trouble getting used to split mode because the halves move around slightly and my muscle memory doesn't know exactly where keys are. I tend to leave the halves together.
I had the same questions before I got a mechanical keyboard without the F row and an ESC key but I got around that pretty quickly. Using the number row with the Fn key for the functions is not bad and I was able to remap the CAPS LOCK key to be my ESC. Works pretty well for me and I was back to pre-mk productivity levels in a short time.