We used clomid both times to conceive our boys. I did 3 cycles with my first. 5 cycles when ttc #2, but ended up having to switch to femera with an IUI and ended up preggers on first cycle. My doctor said that there was a 10% chance of having twins while on clomid, but from what he has seen people who have twins while on clomid have twins that run in their family so he wasn't convinced it was the medication.
But since clomid does induce ovulation you can have a chance of releasing more than one egg. We were nervous every cycle, but had singletons with each. I'm not sure about the hyperstimulation as i never had it, so can't help you there. If you're being monitored while on clomid (our doc did ultrasounds and blood draws), then I would assume the risk is low, because they will stop you for a cycle or two if they see the signs of overstimulation.
I hope this helps. Good luck to you.