Ya never trusted collars on dumbells. I found pair 40s and 60s at Dicks I picked up today. I'm not planning go heavier so can just preexhuast before using dumbbells and do higher reps.
I've had the Gold's Gym version of the adjustable dumbbells for probably 15 years, they work great and served me well. They started falling apart just before Covid hit. I was about to order the Bowflex version but decided to hold off. Now I wish they didn't since they were around $350 prior to Covid and are going for over $1,000 now. I'll wait............
I actually prefer the power blocks to normal dumbbells for some moves, like when you are doing renegade rows or any move holding the two dumbbells together.
I've got the power blocks and they are great up to 90lbs. I have the add on rails to 130's and fully loaded are pretty awkward. Don't get me wrong for a home option they can't be beat for cost as craigslist usually has them reasonable. I paid $500 for mine plus the add ons and a stand. Would have been triple that for stand alone db's
I have Core Fitness adjustable DBs, and they've been amazing. Really easy to change weights, just click the handle. They're flat on the end so you can rest them on your legs. Ive only had them a couple months so we'll see how they hold up over time.
I also have olympic handles, but they're such a PITA to change weights and get into place, I rarely use them.