Just my experience as I started from a similar background. Some weeks ago I had the urge to try TWM myself for the first time. Long time DE user, mostly Ubuntu and switched to fedora some weeks prior. The way I did it was to install sway on top of my fedora installation (with gnome). This way I could and still can choose which session to start at login. And it gave me the opportunity to work out some things using gnome until I grasped what is going on and needed in sway. Over time I was able to build up my sway settings/apps that now I would feel relatively safe use it without a DE installed parallel. Next fresh install I will probably skip the DE and just use a TWM.
Bittä und Dankä!