I'm in a similar situation as
@mwd: in a duo (keys & guitar) with all else as backing tracks. In our case it's all iPads with the BandHelper app as the foundation. It's a lot of work to add each song (produce the backing track, program lights, efx, etc.), but once added a song is 'forever' ready to go. For us, who are of 'advanced age' and just having fun with some local gigs, its a great way to have a decent full sound and cover a wide diversity of styles with the simplicity of a compact setup.
I've found that the more effort you put into producing backing tracks yourself (whether from scratch or starting from commercial MIDI files), the better the results. All our tracks are ultimately produced (using a DAW) as .mp4 audio (with companion MIDI files for lights and fx control, such as Axe scene changes, etc.), maintaining lots of dynamic range. In addition to covering all the instruments we don't play live, if a song benefits from an extra vocal part, guitar part, etc... we just record that into the backing track.
Long ago we used to use laptops, but we prefer the iPads.
Philosophically: when we started using backging tracks (decades ago, it was with sequencers), we were worried about the authenticity of it all, even though we're individually still playing and singing the same thing we used to play in a full live band. Over time we've realized that nobody cares as long as the visible humans are really performing, having a good time, and it sounds good.
