max elements in array

Hi !

I “can have” 1048576 max elements in vertex arrays and in index arrays. Would that mean using exact number or below number would imply “maximum” performance ? What can I expect if I do bigger arrays ? And if my arrays don’t use so much elements ?

Can I also expect same behavioral results on “any” cards ?

Finally and if answers could be different from one card to another, what is the “better” way to do ?