I used to do a lot of snatch grip deads off of an aerobics step. After a while, they were getting so heavy that it was putting a LOT of pressure on my lower back, so I stopped doing them. I was up to 475 for 8 IIRC. I always used straps for these. I think I got a good bit of carryover to my deadlift and squat from them.
I think everybody should try overhead squats for at least a few weeks. They may not make your legs stronger, but they’ll teach you to use your muscles in a whole new way. You’ll train yourself to use your entire body as a stabilizer. I used to do them at the beginning of every workout for one or two sets of 10-15. I always wanted to do bodyweight for 15 reps, but never got up that high. The most I did for 15 was 225, I think.