Can you record to MP4 format, with Audio and Video ? Yes.
IS OBS Studio the right tool for a simple screen recording? typically not, OBS Studio is complete overkill, with lots of power and flexibility, that makes it a bit complicated for beginning users (why use a tank, when a fly swatter will do?). Doable, but I'd start with Why? Why not use Windows Recorder? or something much simpler
As for Recording to MP4. Yes, you can' but don't. Typically MP4 is a unsafe Recording format... any glitch you lose everything. Hence, default is MKV. You can set OBS Studio to auto remux to MP4 when recording is over. (on my SATA SSD, a 1hr 15min 11GB Recording takes maybe 15 seconds to remux to MP4).