I've been doing modding on the deck with just the deck.
So I've run mods on a bunch of different games which were downloaded and installed with the deck alone. No man's sky, lethal company, Subnautica, etc. with generally no problems but some modding software run through wine had visual bugs but the games worked as intended.
So I thought I'd try something bigger and install fallout ttw. I installed the base games from gog without issue, and MO2 ran fine with my overridden default of wine-ge. Even the ttw installer seems to work... slowly. I started it two days ago and the picture is now. I guess some mods you really are better off using a beefier computer and transferring the final product.
Good luck. I tried to do it on my Steam Deck but I think it errored out. I also tried transferring the files after installing it on my desktop but ran into some issues.
I ended up having to use Gnarly's Repack and I think it took a couple hours instead of days
I was ready to stop it and download that but it's the previous version so I'll let it finish. My desktop is currently sitting in parts pending some 3d printed stuff to fit everything together so I've been getting by with the deck and a Thinkpad
Update as of today o clock.
The only other running comp I have is a haswell i9 in a Thinkpad, and after a brief test and ratio math, it's marginally faster only accounting for the first 8th, but would still finish second due to the late start.
Edit: dec11 update.
In the morning it was just over half and when I got home after work around 5 it was done. The first two thirds I guess are the audio reencoding judging by the several oggenc.exe listed in btop. After that the remainder completes in an unknown but much faster time than everything before it. Finished everything else as per the best of times guide with some Linux adaptations. Game seems to run fine and the verifications at the end of the guide worked.
I used bottles, flatseal to allow access to a separate download folder for MO2. Both games installed in the same bottle for the TTW 3.3.2a installer, and fallout3 uninstalled after. Linux version of 4gb patcher used. Fallout launchers were automatically listed in the bottle after installation and MO2 was added via add shortcuts button. Some MO2 downloads needed to be paused and resumed to start and complete but they worked after that.
So it can be done, but the ttw installer would be better done on a CPU that can clear the audio encoding faster than the deck. It would also not require the installation of fallout 3 on the deck itself if doing the mod on desktop and transfer method.