Well I would go off topic if I start on Snapshots. lol However I believe you need a bit of guidance to avoid repeating a non-restore situation and I want to help.
I will respond to your question, but for any further information the answers will be found elsewhere in a few days or weeks.
That being said, you would have had less problems if you had enough snapshots to restore from, so it's a bit related.
It's not the 1st time I would like to refer someone to some sort of tutorial/explanation on snapshots and how to use them to prevent system breakage and rollback.
I will search the Forum and see if this exists already, if not I am very tempted to create one myself and use it for future references. Snapshots can save your system so they are important.
In the meantime, my suggestion is you at least increase the number of snapshots Snapper automatically takes. Hourly, Daily, Weekly, Monthly, use how you feel comfortable but make sure the number of PACMAN snapshots should be sufficient for your usage (default is 10 now, when activated). I would recommend to use 10 if you have disk space for it.
Then if something breaks, you restore a previous snapshot of root (@) and you are back on a clean system, giving you time to discuss here with people and search the web about your problem, rather than try to fix it in a hurry and make things worse.
As for applying the changes within a Snapshot before you apply on your main subvolumes, I have to understand better how Garuda uses Snapper by default, my test bench on a fresh Garuda install does not return good results at the moment (weird). This would be part of my potential tutorial if I can't find one. I don't use Snapper myself so I have to learn.
Again, plz increase your number of Snapshots, especially Pacman (assuming you have enough disk space to handle) and try to have at least 1 Snapshot taken per day, if you use your machine every day. This way when you need to restore you can chose any day and you don't need to think much about "what am I going to lose if I restore an old backup from 2 weeks ago?".
Don't worry, I learned the hard way many times too! Snapshots and external SSD backups helped me learn a lot and also saved my life countless number of times (much less now cuz I better master my system after learning the hard way lol).
Now back on TOPIC, have you fixed your issue?
You installed on a 2nd SSD and it's fine. Do you consider this topic solved, then?