You can play whatever you want, it just gets reencoded if it’s not AAC already.

Yes, too many variables. The most important thing is the bluetooth implementation. My Xiaomi android TV has a different latency every time I connect.

Depending on the implementation, the latency can be reduced by tuning the aptX settings (which the gaming mode does) but if those are fine and the latency comes from somewhere else, it won’t help.

In general, chinese devices and anything from Samsung are bad in this regard. Other phones tend to be better and the steam deck has been excellect for me.

If it has one/two 3.5mm jacks like the A40, that depends on the sound card. Nowadays all PCs have built-in ones that are about as good as what’s in a playstation so you’ll have to try hard to hear a difference. You might need an adapter to switch between the single 4pin jack and dual 3pin jacks though.

Bluetooth is a mess for headsets so avoid that. The proper wireless ones come with a dongle and have the same quality on all devices.

The WH1000-XM4 (over ear) has the ability to do a scan and tune the ANC automatically, you trigger it by holding down the ANC button or through the app. Doing that made the ANC much more comfortable for me. Maybe the WF also have that.

I upgraded my XM1s to XM4s and was disappointed. You can’t use LDAC when connecting multiple devices and the headphones need to reboot when switching modes. They also don’t sound any better than the old ones and just have a slight advantage in comfort.

I’d say go look for something else.