Once you tell us how many watts the bulbs are, the question can be answered.

Let's say 75 max.

A 15A circuit at 80% utilization is 1440 VA (for all intents and purposes here, watts). That's 19 75W bulbs. Actually, I think the biggest you can put in an H3 is 50W, so in that case you'd get 28.

Turns out it's a 150w max. The sticker has several options that I thought were all the different models - turns out it's the different kinds of trim and you can use different bulbs with certain trim.

The max bulb with some version of trim is 150w.
Therefore, I need to wire for that. Kinda stinks.

Why are you worried about the worst case scenario?

If you are worried about some unknown person in the unknown future switching out your LEDs for the max incandescents possible, the worst case scenario is that the breaker trips and they realize that they can't do that. It isn't going to burn the house down or anything.

It depends where he is in the country. In some places he may run into inspection issues, of course some places with strict energy codes wouldn't allow fixtures you could take the efficient bulbs out and replace them with the heat generators at all.

It's an inspection issue. I pulled a permit and I'm doing it right.