Another possible build is to use a mini-pc and M.2 connections

You'll need a mini-pc with two M.2 slots, like this:

https://www.amazon.com/Beelink-SER7-7840HS-Computer-Display/...

And a riser like this:

https://www.amazon.com/CERRXIAN-Graphics-Left-PCI-Express-Ex...

And some courage to open it and rig the stuff in.

Then you can plug a GPU on it. It should have decent load times. Better than an eGPU, worse than the AM4 desktop build, fast enough to beat the M4 (once the data is in the GPU, it doesn't matter).

It makes for a very portable setup. I haven't built it, but I think it's a reasonable LLM choice comparable to the M4 in speed and portability while still being upgradable.

Edit: and you'll need an external power supply of at least 400W:)