Yanks VR review
Yanks VR lists 180° stereoscopic videos and 360° monoscopic videos in the same catalog. It also offers a free sample download so viewers have a file to try before looking at membership.
Depth and coverage are separate choices
The 180° titles are described as 3D, while the 360° titles are described as monoscopic. A wider view can therefore use one image rather than two eye views. The WankitNowVR review explains how projection and stereo layout appear as separate player settings.

Try a file before filling the headset
The Meta device guide describes downloading to a computer and transferring the file to a headset player. It uses Pigasus as an example and also mentions visiting the site from the headset. The sample gives viewers a smaller first step than choosing several files at once.
Anabel’s take
I’d use the sample to check how my player handles the format. The distinction between depth and full-circle coverage is the most useful thing to keep in mind when choosing a title.