Gwern Gof Uchaf is always open.
The North Ridge of Tryfan is a classic grade one scramble, and I highly recommend it. You can get to it by walking up the track to Milestone buttress, or more interestingly, you can start it from the other side of the wall where it comes down to the road.
If you want to do a climb, First Pinnacle Rib and Grooved Arete are both V Diff classics. Grooved Arete is the harder of the two, but First Pinnacle Rib includes the "interesting," notorious and avoidable yellow slab.
The descent to Bwlch Tryfan is not hard, although you just need to watch the route finding a bit, and be prepared to back off and find another way if you aren't comfortable.
The continuation to the Glyders and over to Y Garn via Bwlch Tryfan is straightforward and popular. You'll need to allow plenty of time, but you can escape at Bwlch Tryfan or down the Gribin Ridge if time becomes an issue.