I also had similar concerns. Their voyager keyboard should solve that concern and I’m strongly considering using it. I’ve had their Planck EZ for maybe 2 years now (on Dvorak) and later got their Moonlander but I think it was too much for me and went back to the Planck shortly after.
Ben Vallack has a good video on the voyager[^0] and many other setups and workflows
I personally find the two large buttons in the thumb clusters to be easy to access. I don't think the entire thumb cluster is designed to be used commonly while touch typing. There are plenty of pinky reachable buttons you can map needed keys to.
