I've switched from a 2018 Mac mini to a Mac Studio recently, no improvement in Bluetooth stability. Sound in AirPods Max occasionally is garbled for a moment and both my Magic Keyboard (the old one with batteries) and my Magic Mouse 2 sometimes lag or completely disconnect and reconnect after a few seconds. Also Unlock with Apple Watch (that work with a combination of Bluetooth and Wifi afaik) is kinda unreliable (works best when I hold the watch right next to the Mac Studio).
There are days when it's perfectly ok and others when it's almost unbearable (especially audio). There are a lot of factors that seem to make it worse. Exact placement of the Mac (which is about 30 cm behind my mousepad), cables connected to the Mac (especially USB 3.0), an iPhone standing in a Qi charger right next to it, stuff laying around on my desk, and so on and so forth...
I've also suspected the very crowded 2.4 GHz spectrum here, but interestingly, there is absolutely no problem with Bluetooth audio with both my iPhone and Apple TV in the same room, it's just rock solid there.