I've attempted suicide by overdosing propranolol before. At the time I was 5'2 and roughly 135~ lbs. I can't remember the exact amount I took to overdose, but I believe it was under 28 of the 10mg tablets, though over 20. I experienced intense visual hallucinations roughly an hour after ingesting the pills and saw insects everywhere I looked. I was taken to the hospital, where I was kept overnight however received little to no treatment. The hallucinations ceased by the time I was released from hospital (the following morning).
I would have taken more, however I am unable to function as a regular person and therefore live with a carer who collects all of my prescription medication for me, and stores it and any other pills in a safe space to avoid me taking them in attempt to harm myself.
If you're planning on this method, you'll need to take far more than what I did for it to be successful. I'd recommend doing your own research, and having input from those on here who know more than I do.
I hope this helps!