I don't know why anyone would say this. If you don't plan to use LND as a public routing node, you can install the whole stack on your personal machine if you have the space for it. Bitcoind+Electrs+Tor+LND for the core. You can turn your computer off and come back to it whenever you want with no real penalty except waiting a little bit sometimes for the blockchain to sync up.

To the other question about hardware. Linux will generally and happily boot no problems. If any config files have any hard coded drive paths anywhere that might be a problem but I don't know if Linux would change the drive path on new hardware. It might depending on the slot the drive is plugged into.

it is always better to do a fresh install and migrate data if you can. The bulk of the data is for the blockchain database and electrs database. The rest can be reconfigured from scratch pretty quickly.

You have all the extra hardware as is, don't waste money. Just do it and see if it works. If not then upgrade. Don't be hesitant to experiment with what you have for things you might not really need.