Are you talking about laptops here? I think the main system people usually use to run full nodes is their PCs not laptops, I don't even think it is efficient to use a laptop since you can run a PC for long periods even 24/7 but not a laptop.
A PC motherboard supports multiple storage disks (SSD, M.2, SATA).
Yes and no. A lot of people run 'headless laptops. You disconnect the display and remove the battery and just have the base of the unit plugged in.
I have a few like that. Most recent laptops also have either 2 x M.2 or 1M.2 and 1 SATA
The advantage is that there are a lot of laptops with broken screens out there that are just not worth repairing. Once again looking at the 6th gen era.
But, for $100 + a drive they are cheap.
I see them pop up on Craigslist / freecycle and such all the time.
Obviously, YMMV in different parts of the world.
-Dave