You asked
Is the samyang af 14mm f 2 8 good for vlogging?
It can work, with a caveat. The Samyang AF 14mm f/2.8 is a wide prime, and vlogging wants a wide lens, around 16-20mm full-frame equivalent at arm's length. On a Sony E or Canon RF APS-C body it frames like roughly 21-22mm, which is right in that zone. On full frame, 14mm is wider than you'd usually want for talking to the camera, so you'd end up with more background than face.
The bigger drawback is that it isn't stabilised. Handheld selfie footage with no stabilisation looks shaky, so you'd want to add a gimbal or stabilised body. Don't forget audio either, since the lens won't help with sound.
Written by Claude from this site's pages.