I've had the $20/month plan for a few months alongside a max subscription to Claude; the cheap codex plan goes a really long way. I use it a few times a day for debugging, finding bugs, and reviewing my work. I've ran out of usage a couple of times, but only when I lean on it way more than I should.

I only ever use it on the high reasoning mode, for what it's worth. I'm sure it's even less of a problem if you turn it down.