Bird & Breakfast can be played solo or with a small group, and while slow-paced also isn't terribly long. Probably 2 hours at most?
you are an earthworm who aspires to kill god has one principal protagonist, but can be played with any number of players cooperating to run them. It lasts somewhere between 15 minutes and until the end of time.
Initiative is more of a tool than a proper game, but in terms of time commitment it's probably a little shorter than your typical combat encounter in any other game. It supports three players and a GM by default.
Explicit Course is a party game, and as such seats as many people as you can convince to tolerate each other, but probably isn't fun with less than four. A round will probably take about 20 minutes, but the fun's in the time spent talking afterwards and it can easily be run a couple times in a row.
Lastly, A17-Q Declassified is a tormentous exercise in boredom, and should not be attempted unless you have way too much time to kill. It supports up to six players, but I suspect there's probably not six people on Earth who would genuinely enjoy this game beyond laughing at the concept. I happen to be one of those people. If you're another, please, please god get in touch with me.