do i lift heavier weights or not?

i keep hearing different things.

smaller weights with high reps= tighter toned muscles

bigger weights with less reps= burn more calories, more muscle definition, burn more fat

i'm naturally athletic looking so my arms are already too defined. So does that mean i should use small weights since i want my arms small?

but if i do that does that mean i don't work out as effectively since i'm not burning as much?

what do i do if i just want strong toned feminine arms?
do i lift heavier weights or not?
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