SSD is soldered. But more than that, the storage controller is built into the SOC and the SSD is just plain flash memory. So even if you manage to swap it out, it will not work.
With the M series, they went full on non-standardised parts.
There's a learning curve when you switch from Windows to Mac. You'll eventually get used to it because all shortcuts are different and how things work in Mac is distinct as well.
My friend who works for that green logo company been given a dell precision laptop. I wondered how much his config would cost. So I built it on Dell's site. With lovelace 3000 GPU and 128GB ram it came to f'ing 10L. I asked my friend how much is the battery backup, he happily said it's around 4 hours. He never had a laptop with this much of battery backup before.
Coming back to your point, yes, the base MacBook Airs do look enticing. But the rest of Apple's lineup is also not bad if you have a use case for it. We can have a 6L MacBook Pro that outperforms my friend's 10L Dell Precision in almost every department.
There's a void of serious-serious high-end business laptops in the Windows ecosystem.