What's the germination percentage of the seed?

Near 100%, 1 per pot should be fine, and then replant the few that didn't grow.

At 80% or lower (most seeds), double or triple plant if you have the extra seeds. Once they sprout, remove the weaker sprouts using a cuticle scissors to cut them at the base. You don't want to disturb the soil at all as new sprouts are delicate.

Remember even 80% means that, out of 100 pots, 20 won't grow if you single plant. 4 won't grow if you double plant. There's a 1 in 3 chance (or so) that 1 won't grow if you triple plant.

My home-gathered seeds range from 36% viable (red salvia) to 88% viable (red celosia), so there's a very wide range. The salvia will be planted in fives. The celosia, threes. Most others, four.