The layers where not the biggest issue to be honest, it's like using the shift key, except I have 3 more "shift" key, plus the actual shift key. It took me a couple of days of use to get my symbols layer commited to memory.

And changing keyboard if you do it frequently is not an issue, especially if they have different layout.

It wasn't so bad, switching to a different letter layout was way harder

It took me a couple months to stop thinking about layers.

My first move toward ergonomics was a Keebio Fourier 40%. It had been a few months before that when I started using Colemak on my laptop keyboard; I did that using Windows keyboard settings, and I was taking notes in meetings, so whenever I couldn't keep up, switching back to QWERTY was a hotkey away.

After switching to the Fourier, and iterating many times on the QMK settings, that was the month or two where I had to think through all the control keys, symbols, and function keys I was typing. I didn't quit typing on other keyboards, although I typed on my Fourier as much as possible; and I have not ended up forgetting anything I learned before.

I'm now on the precipice of moving from a 4x6 Dactyl Manuform to a 4x5 Splaytyl (if I can find those dang parts and get the thing built!) and that's too small to have things like Tab, Enter, or the backslash on the home layer. I'm nervous. I've tried making a 4x5 layout for the DM, but haven't ended up sticking with it. I couldn't really get used to keys that are physically there, not doing anything.

Wait, you're supposed to adapt? I just fumble my way through the day.

Mine isn't even that reduced and after 4 years I still miss instant, layerless access to the F keys.

My strategy was to make a mental note of where my fingers expected the key to be and then map them to a layer later. That was I wasn't working against already engrained muscle memory. It helps to have layer themes too. I have alpha, numbers, and coding symbols.

It took me a few weeks to really get to muscle memory, but after that I disliked full-size keyboards enough that I started using kmonad on my laptop with the traditional keyboard. I eventually ended up with kanata (which has a superior chord handling) everywhere, until I got a piantor 50%, when I switched to QMK.

I switched by degrees, though; I'd used a more limited set of layers for a couple of years before going full gonzo, so I was used to the modality; adding more layers was less a new paradigm and more just adding complexity to what I was, by then, familiar with. So I can't say I'm a fair measure.

QMK has been a struggle to get all of the settings working such that there isn't some behavior that is annoying, and I'm still not there, but having the programming in the keyboard has made some situations easier (consoles, etc).

I'm 9 mos into the piantor, and I still struggle with remembering where I bound some infrequently used layers, like the layer I put all the F-keys. And rarely I'll think about how to get a key - rather than relying on muscle memory - and simply fail to remember the magic combo. However, I won't voluntarily go back. Having numbers and special characters accessible without having to change my hand positions is simply invaluable, and I still use kanata on my laptop to get the same behavior, despite it meaning I have a whole row of keys I'm not using anymore.

The biggest hassle in going back to a full size is the reduced number of thumb keys. And I admit, I learned to touch type being able to hit the space bar with either thumb, and simply do not have the luxury of enough keys to dedicated to duplicate functions to allow this. This would be probably my biggest complaint, and only regret about switching.

I kept a standard layout keyboard handy for about a week, it took me probably 3 weeks to transition fully. I fall immediately back into bad habits of typing on both sides of the keyboard on standard QWERTY keyboards without the ortholinear split layout, sometimes I even try to reach across the split after a day or two and hit T or Y with my index finger from the wrong hand.

I've got a 42 key cantor at home, previous keyboard was Logitech K860. At work we get these standard full sized keyboards that come with the PCs we order. I've had no real issues switching, apart from the first two days of getting used to the layout. Sometimes I'll hit the XCVB keys wrong, but that doesn't bother me too much.

If it's the only way to press the letter / sign / number you need, you remember pretty quick.

I think you'll end up going layers on your everyday after you do it on your "other" board.