With thunderbolt you can connect it whenever you please. Your OS doesn’t initiate the thunderbolt connection until it’s in the operating system anyways. Plug it in, turn it on it makes no difference. Disconnecting you need to make sure you safely eject the device or you will get a blue screen.

M.2 adapters are almost never hot plugable, those need to be done with your laptop off. That is literally the same as having a desktop and slotting in the card there. Just make sure your enclosure is off when you’re connecting or disconnecting anything and you won’t hurt anything.

bifurcation Is the keyword you’ll want to be looking for. And before you look into it any further make sure your motherboard even supports it on that slot. Bifurcation has existed since like pcie2 or something, but just like rebar hasn’t supported on consumer platforms until pretty recently.

That said I can’t actually help you because I don’t know of anything to do this. I can only imagine it doesn’t exist because there’s not enough space on one M.2 slot to fit two M.2 ssds. Traces take up space, connectors take up space, and you’d have to somehow double stack SSDs on top of each other and they already get too hot for their own good.

LPDDR is more than just low power, it’s also higher performance. Even at higher power draws DDR5 in sodimm factor can’t compete with LPDDR5.

ex: On the Thinkpad T16 Intel gen 2 regular DDR5 runs at 5200mhz, on the AMD equivalent with LPDDR5 it runs at 6400mhz