I find that changing the layout creates significant mental overhead for me as well, so I just don't do it. I use the NEO layout [1] which contains all the characters and symbols I could possibly need in reasonable locations. I barely need to leave the home row to write any of the symbols needed during programming or writing TeX.
As for physically different keyboards, I've found it to be a much lesser issue than I expected. I recently got a Moonlander [2] due to general hand and wrist pain that could only be attributed to strain from typing.
I took care to map the layout quite closely and the physical layout was almost immediately usable. I started at around 2/3 my normal typing speed but was back to 100% in a matter of a week.
Going back to a normal keyboard takes minimal effort. I can still type on them quickly, I just loathe them more than I did before now that I know how much more comfortable it could be.
As for physically different keyboards, I've found it to be a much lesser issue than I expected. I recently got a Moonlander [2] due to general hand and wrist pain that could only be attributed to strain from typing.
I took care to map the layout quite closely and the physical layout was almost immediately usable. I started at around 2/3 my normal typing speed but was back to 100% in a matter of a week.
Going back to a normal keyboard takes minimal effort. I can still type on them quickly, I just loathe them more than I did before now that I know how much more comfortable it could be.
[1] https://neo-layout.org/
[2] https://www.zsa.io/moonlander/