Can I use one eGPU on both laptop and desktop?
Can I buy a eGPU with M.2 connector and connect it to a M-itx PC, and use M.2 to Thunderbolt gender to connect to my macbook air?
When I use M.2 to my PC, does it uses more than 4 lanes?
I heard thunderbolt can decrease the performance because it can only use 4 lanes.
And if I can, is there anything works like a swith for M.2?
+ How can i make a pass-through charging system with only one Thunderbolt cable?
If the PC only has M.2, then you can use a M.2 eGPU for the PC, and use it with the Mac using a Thunderbolt to M.2 adapter.
The ADT Link R43SG-TB3 contains both the Thunderbolt to M.2 adapter and the M.2 to PCIe GPU adapter.
M.2 only has 4 lanes = 31.5 Gbps for PCIe 3.0 and 63 Gbps for PCIe 4.0. In either case, probably only ≈75% is usable ≈28 Gbps (3500 MB/s for PCIe 3.0 and 7000 MB/s for PCIe 4.0).
The ADT Link cable might not be good enough for PCIe 4.0.
Thunderbolt 3 is limited to between 22 and 24 Gbps (2750 MB/s - 3000 MB/s).