I’m sure there’s probably some sort of mdadm invocation to shrink an existing RAID1 mirror pair, but in the absence of that, one option is to create the mirror pair you want on your 2.5" SSDs, and then shrink-and-clone the filesystem from the NVMe mirror to the 2.5" SSDs, using something like Gparted.
In that way, you end up with the mdadm pair that you wanted, and the filesystem is correctly sized. You can even clone the UUIDs for the filesystem so fstab entries won’t have to be changed.
This is a shorter answer than I typically would write, but any sort of exercise program should be atuned to your specific circumstances, since if it’s not practical to execute upon it, then it’s not going to sustainably achieve its objectives.
As for me personally, I wrote my program based on a friend’s five-day-per-week program, which splits the days into: arm day, back/shoulders day, chest day, leg day, and core day. I specifically do not want to be overworking certain muscle groups without adequate rest. Each day takes no more than 60-70 minutes, including warm ups.
Might I suggest posing in c/gym or c/homegym for advice on how to tune your current program; there shouldn’t be a need for a full rip-and-replace.