It must vary then I can boot 7000 with both sticks and y cruncher stable at 6800 on my 2021 Apex but getting Karhu stable on slot 1 is the challenge. 6400 is easy but 6600 to 6600 is difficult.I dont think the gap is the Problem. Only the max bootable.
My new apex also 400mhz between both slots. But now im able to Boot 7200/7600.
My apex before 6200/6800. Max stable was 6000.
My unify boot only 7000 max. I think if u take the Bad slot -200 u get your max stable clock.
So for me on old Apex a good 400 to 600 below what I could boot. This is with Hynix sticks. Never had Samsung to test.