I’ll try to work through your questions in order:

1. Honestly, this is one of those cases where you should take full advantage of Amazons return policy and buy one set to test, and if it doesn’t work, you can simply return them within the 30 day window and try the other one out. It’s the most fool-proof way of knowing for sure if it’ll work in your particular context.

2. After reading more about the Avantree, I’ve got a concern that their microphone function is strictly intended for recording applications and may not function to transmit audio and voice simultaneously. I’d recommend looking at the Q&A section of the Amazon page and filtering for the word “mic” to read some of the responses.

Best case scenario would be that the Avantree will work for your PC, but I don’t think they’ll work for either the PS5 or Switch since I believe they use USB for audio decoding for chat and these only connect via RCA/3.5mm. This is why I didn’t recommend the Mpow as a transmitter across all your applications since it also only has 3.5mm or RCA connections.

The other thing to note with the Avantree is that it looks like a closed-system. Meaning that they may not pair to other transmitters or receivers and only work with each other. So, it may limit their use between your different gaming devices.

The absolute simplest setup for the PS5 and switch is the creative BT-03 paired to any other receiver AptX LL receiver like the Mpow.

1. The good news is it looks like the Avantree works when connected to a usb power source. So, the unit that is stationed by the PC can use a USB port to sustain power instead of requiring periodic charging. Most of these types of devices work on both battery and usb power, but there are some select ones that don’t. The Mpow and FiiO work on both battery or when connected to usb power.

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One more thing I’d add for your consideration:

1. It is important to consider the quality of your receiver above and beyond the quality of the transmitter. The reason is that the transmitter has only one job—to transmit a digital signal to another device. The receiver must not only accept that digital signal, but it also has to convert it to an analog signal, then amplify that analog signal so it is at an audible level to your headphones. If the receiver cannot amplify the signal sufficiently to meet the power requirements of your headphones, you won’t get a loud enough volume output. Moreover, even if you can get a loud enough volume, if the amplification stage isn’t well designed it can distort the signal and you’ll get audible clipping when listening.

For this reason, I recommend paying a premium for a good receiver, like the FiiO, that focuses on a clean amplification stage. You’ll also avoid needing to upgrade the receiver if you get more power hungry headphones in the future. You can then pair that receiver to a much cheaper transmitter without sacrificing audio quality to the same extent.

Finally, the FiiO has the unique ability to use an in-line microphone if one is detected on your headphone cable. This means you could buy something like this for your Sennheisers, and keep the BTR3k in your pocket since the microphone is no longer tied to the actual receiver. This would allow you to upgrade your microphone if you find the internal one inadequate.

Edit: now that I think about it, I think the most efficient way to solve your setup issue would be to buy the Creative BT-03 and one MPow device, then test using it with all your devices—including your PC. If it works, then I’d say you got the best bang for your buck. If it doesn’t, I’d then return both items and try the avantree setup. If that doesn’t work, you’d have to go back to the drawing board.