You can hit limits with $100 if you use it all day.
You can do it easily if you use in fast mode.
I bet you could hit the limits of the $200/month using fast mode if you were using multiple sessions at the same time all day on fast mode.
The OpenAI tiers seem pretty well tuned.
I used to use the plus ($20/month), and that was good for a few sessions every once in a while.
But now that I'm using it to configure my network, monitoring, maintenance, I'm using it every day and I'm on the $100 plan. And I do pretty consistently hit the limits, but it's easy to pace myself.
I'mam thinking about upgrading to $200/month though. It would be nice not to have to ration it.