3bet from BU = 3bet in position
When opener has a tight or strong very short range like UTG or UTG+ for long tables, the 3betting range should be made up of premium
hands like JJ+ and you can sometimes combine it with suited hands or special blockers. Examples: TJs+, ATs+; KJs+.
When the opening comes from a late position like HJ or CO the 3-bet ranges can be wider: K7s+, Q8s+, J9s+.
The reverse case: very similar BB 3-bet (out of position): mix strong hands with decent combinations and when the opening range is wider defend more often.
Greetings.