There will be very few cases where running a 30Q would be safe but a P26A wouldn’t be. You’d have to be pulling something like 15 amps at turn-on before you’d have a lot of difference, and it would have to be a difference where 20A versus 15A fries something, which is pretty uncommon. Most lights where someone says to use a “low drain” battery, they’re talking about a 35E instead of a 30Q, not a 30Q instead of a P26A.

Don’t worry about it. And unless you’re measuring lumens at turn-on, you’re probably better off with the 30Q. Up at those currents, the lumen difference is usually nearly impossible to discern by eye, mostly just extra heat, and you’re sacrificing runtime.