It depends on their height over the counter and the 'throw' (AKA 'spot size') they give.

Not sure how many pendant lights to put over my 12' island

RL thanks so much! That’s very helpful and it looks good. However, the counter will extend about another 12” on the right side of island. So I think then in a mock-up the one pendant would shift over to the right a little. Still think just the 2 and that they’re a good scale for my space?

Different goals come into play. Task lighting for when you work at the island counter requires 450+ lumens at the surface. The source should be placed so you don't shadow the work with your body. Ambient lighting is another objective. Recessed led cans on dimmers can do both. Pendants on dimmers or pendants and recessed lights can also do both. In addition, pendants can be decorative. Adequate task lighting is often missing in kitchen design.