My 13 Pro Max worked perfectly! My Apple watch 8, Airpod Pro 2nd gen, my Sony Xm5's, and all car's bluetooth would just connect pretty much instantly! There was never any drop in/out, having to reboot to connect, or delayed connecting. It just worked.
I've since had a 14 and currently 15 pro, and they've both had horrible bluetooth and wifi issues. I'll have to put my airpods back in the case 2 or 3 times before they finally connect. Heck it'll even say my devices are connected in the settings then start blasting music from the external speaker when I press play. I'll have to reboot my phone up to twice a day to get my Xm5's to connect. AND my Apple watch 8 will be "connected" but not actually connected causing massive battery drain on it while it's constantly searching for signal. One of the only way's I can tell is when the weather widget stops showing the temp, then if I try to use the watch app I can't see any of my watch's info like how much free space it has, nor can I search for updates cause it's "Not connected."
Still have my 13 Pro Max that's fully updated, after testing it, bluetooth still works flawlessly on the same devices.
This has been an issue since the 14 release sadly and it still doesn't seem to be fixed.