If your speed light has high speed sync, you should be able to go to a higher shutter speed than 1/160, a lot higher actually. Look up how to use high speed sync for your speed light model. Should be in the manual. If your speed light is off camera, then your wireless trigger must also be capable of hss.
What’s AF?
Seriously, I use auto focus for personal shooting and manual for pro but my reason is that I shoot product prototypes that later get replaced with cgi so I have to shoot multiple images of the same shot to get clean plates without product and without talent for later compositing.
If I shot people primarily, maybe I wouldn’t use manual focus much or at all.
Google day for night color grade tutorial. It’s used all the time in filmmaking. If you want it done right, study then shoot. If you are working on a preexisting shot, maybe some of those tutorials will help.
Very often interior night scenes are shot with bright light and looking fully lit but shaping the light matters. Then darkening in the edit further reduces the noise floor in your image.