I stopped using MAQS after a very ineffective treatment in 2019, followed by fobbing off from the manufacturer. All hives were MAQS treated in the Autumn. Late Dec 2019 I did my round of OA sublimation treatment, and was very shocked to find mite drops in the 100's on most hives. I'd call that a big fail for MAQS. They were more interested in covering their arses than investigating the problem. So, that's £800 or so a year they won't be getting from me any more.
During 2020 I tried extended release OA using Randy Oliver's techniques. He has found it very successful in his part of the USA. Sadly, it doesn't seem to work in a humid and relatively cold UK. So, Autumn 2020, everything had Apivar followed by OA sublimation in Dec. Hardly any drop from the OA. This season, I've seen the best brood patterns I've had for years, and where conditions allow, extremely productive colonies.
Sadly, there don't seem to be be very many (if any) effective soft chemical varroa control products. You can keep bees alive with a combination of those methods, but they are unlikely to thrive. lesson learned.....slightly ashamed that it has taken me so long.