Make one a server and run tor/i2p services or self hosted data

I’d have to keep it running all day?

If its only selfhosted software and services you could turn it on when you need the services unless it was something youd need to access from outside your local network then yes it needs to always be running. You could setup cron to auto reboot after a certain time.

Here is what i would do: - install omarchy.org on one and get familiar with playing around with linux. Connecting from one machine to another. Build confidence around the terminal - install start9.com on the other and run some services