My impression was they were also going to try and move the T2 off being a separate (potentially replaceable) chip and integrate it with the M1 - did that happen

My impression was they were also going to try and move the T2 off being a separate (potentially replaceable) chip and integrate it with the M1 - did that happen yet or still to happen? But one thing you get on a mac is basically hardware level security for the SSD. Bad news, data recovery will be hard / impossible. Good news, if you sell the thing on pretty unlikely next person will get your data or can remove the "drive" and try to crack it offline. Not sure how imaging a mac drive works these days either?