Help! I don't like my Recaro Seats (2021 Mach1)

Your best bet is to sell the car and order another one without the recaros. If you try to modify the seats, you can screw them up and also hurt the value of the car. If you try to swap them out for regular seats you may not get the heat/cool function to work and you will hurt the value of the car. And finally if you swap them for regular seats out of a GT you will lose the mach 1 stripe on the seats and hurt the value. Just sell the car as is and get another one the way you want it. Ask the dealer what he will give for an outright sale not a trade, and try the various online places like carvana and vroom and see what the will give you. Hopefully some one will give at least what you paid. Two months ago you could have made a couple grand profit with the chip shortage driving up used car prices. Even now you could still break even.

BTW, I'm 6'3" and about 350 lbs and I fit in regular premium leather seats in my 17 convertible, not great but it works. My car is only a toy, I've only done 13K miles in 4.5 years of ownership.

And finally, unless you are going to track the car, there is no point in getting the recaros, unless you want them for bragging rights.

OP is not a small person and frankly just doesn't fit comfortably.