I ran a 1x9 for a while, with a 44 in front and a 12-23 cassette in the back. The point was simplicity, getting rid of a lot of redundant gears.

Basically I removed all chainrings from a road triple and replaced the middle one. I picked a gearing combo where I would use the full gear range, and where the 44 x 16 combo that I used most often was in the middle and had a good chainline. I probably over-thought the whole thing, but it worked extremely well for my purposes.

I'm assuming that using a non-ramped/pinned chainring helped me avoid throwing the chain very much, but it did still happen rarely if I hit a decent sized bump/ramp too fast or went too quickly from smallest to largest cog in the back.
I never used a chainguard though.