Plus Size Mattresses?

Hey all, I'm having terrible sleep on my Simmons Beautyrest Black Hybrid mattress. We have had it for approximately 2-3 years and the sagging is real. Constant back aches, tossing and turning, haven't slept well in ages. I've been doing some research on mattresses designed for plus size individuals like myself (around 275-285 lbs) and there's more out there than I realized.

I've thought about the WinkBeds Plus, Helix Plus, Saatva, Big Fig, and Dreamcloud mattresses but I was leaning toward Helix Plus as I've seen reviews of it holding up and not sagging, even after a few years.

Does anyone have any of these mattresses and swear by them? I'm hesitant because I have always had a tough time with mattresses and they're always such an expensive investment with a crappy return.

Thanks!