There is no point being DRM-free when you have thousand of games. Or someone here really keeps their installations locally?
Time to share some of my autistic behaviors with the Codex.
This is my entire folder of GOG installers. Currently at 108 games and growing at a very slow pace. I don't hoard a bunch a games like most people in here do, and I tend to be very selective of the games I want to keep. Although I have a Steam account, I haven't used it in a few years, and the games that I really cared about I have repurchased at GOG with big discounts. About a dozen or so of the games I have on GOG came from the free giveaways.
Here are the worst offenders in terms of installer size. I keep them all up to date with gogrepo (for which I have mode some modifications myself). The entire library is also backed up on an external HDD, my home server, and on a remote location using Google Drive (encrypted to be on the safe side against Google's scanning of Drive contents). I keep it all in sync using rclone.
For actually managing the games, I initially used Galaxy, but then ditched it in favor of Playnite. All my GOG games are registered on the local Playnite database (which is also backed up on an external drive, home server, and remote location). The metadada of each game (along with icons, background images, etc) is obtained through Playnite itself using the GOG game ID, available from gogdb.org.
I have configured each game with relative install paths using folder junctions within Windows. This makes the installation of each game independent of where the game is actually installed at (my ssd or hdd, depending on the game). Moving the game from one place to another only requires updating the symbolic links, for which I use a small script for automating the entire process. Playnite only sees the relative install path of each game, making the process of migrating things around and restoring my setup at another computer a breeze.
Lastly, I have recently implemented a C# application for managing the backups of saves/settings of all my games. I have also implemented this application as a Playnite extension for simulating the cloud saving behavior of Steam/Galaxy, albeit with more functionality. Upon closing any game, the extension backs up the games data to the specified locations for safekeeping, e.g., my local backups drive and Google Drive, so that I also have an up to date remote location with my saves.
The benefit of my approach is that I can backup the saves/settings of any game, even those that Steam/Galaxy do no support. Children of Morta is only an example where the save data is in a regular folder, while the game settings are in a registry key. With my program I can back it all up and easily restore the backups whenever is necessary.