You are mistaking what 'stereo' really means. Take one mono track and pan it full left in your DAW. Take another mono track and pan it full right in your DAW. Now listen or export the track as a stereo WAV file.
Why limit yourself to 8 tracks if it is not a hardware limit? A lot depends on the type of music you are recording, of course.
On a typical rock track, I have drums on 7 tracks (overheads on a stereo track, the others mono + a reverb bus), bass (I may track it twice), keyboards (piano on a stereo track or organ on a mono one), 2 or 3 rhythm guitar tracks (one may only be on a bridge, or chorus, for example), lead guitar track (I usually will record at least half a dozen takes, and use separate tracks as I find it easier to work with tracks rather than takes in Reaper) + instrument reverb bus, lead vocal (I may comp from as many as 4 separate takes), reverb track for it, backing vocals and/or harmony tracks + reverb bus.
An 'acoustic' song will have at least 2 acoustic guitar rhythm tracks, lead guitar (multiple takes), bass, strings and vocals and reverb busses.