Is it a good choice to archive game files to an external DVD? My SSD is in short so I need to make more room for the games, which eats up the storage.

Sorry, we don't know. The topic of discussion here is how to make new games, that is, we discuss games that don't exist yet.

We have no information about what you can or cannot do with a game that is already published. You may want to ask this at the publisher of the game you want to move.

You can try this:

https://github.com/ImminentFate/CompactGUI

It's a tool to compress any kind of data, and it has been reported to work well with games. (Have not tried myself)

If you get an iSO file , you can burn it to DVD ,it won't take up much of room .

Just do that like this tutorial .