Stereo tracks get frozen as stereo, mono as mono. They can be switched from one to the other using the track interleave button as savoy says.
Recording drums is a huge topic on it's own.
If I were recording a real kit I'd be inclined to start by considering using the Glyn Johns method. Just four mics positioned for the best sound and fewest phasing issues. Assuming the kit's well balanced for volume and tuned of course - if it isn't that needs sorting out before any tracking gets done whether there's one mic involved or 20+. If the drummer isn't well balanced for volume, that's a different matter :-)
Drum soft synths/samplers don't offer that method, and the mic placement is wherever it was when the sample was recorded, so I generally "track" each part of the kit separately in mono. Maybe put the toms through a stereo channel, maybe the cymbals, but treating each individually and routing them to sub-group stereo aux tracks which then route to a drum bus works for me. It makes doing surgical eq to remove narrow-band resonances much easier. I usually pretty much ignore the sampler's "built in" mixer and effects and just handle the outputs like any other audio.
Drum machines I either track in stereo or each sound to its own track. Or the kick and maybe snare, claps and hats get their own tracks to make processing easier.
As for synths, which for me are mostly hardware, generally I track them in mono even if they have a stereo out. That way the track can control stays as a pan, not a balance control. Unless I've a compelling reason to track one in stereo - e.g. my MicroQ has two filters which can be placed in parallel and panned differently plus its own effects so it gets tracked in stereo, or sometimes I might decide to sequence a synth's stereo pan so some notes come out panned differently to the rest.
Whatever seems like the best idea at the time basically.