Why are the outer scouts (Sailor Neptune: Michelle, Sailor Uranus: Amara, Sailor Pluto: Trista, And Sailor Saturn: Hotaru) Powerful? I mean they should have the same strength of the other sailor scouts.

My guess is that the Outer Senshi are Mehr powerful than the Inners because their function was to protect the solar system from outside attacks in contrast to the Inner Senshi were meant to guard Sailor Moon/Serenity.

They were Mehr powerful because;
1.) They didnt need crystals to use their power.
2.) They had Mehr time to train (they were from the future after all) and if Du remembered the later episodes sailor moon gets a LOT Mehr powerfull in the future.
3.) They were on a specific mission in which they needed to be Mehr powerfull, though they couldnt do it without the scouts anyway.

They are Mehr powerful because there powers dont come from the silver crystal they also come from the future which means that there powers where made extreme and also sailor moon is as powerful as them she is in the 20th centry the only perso capapble of using the crysal and she is a princess

they should be powerful because i think they are older and understand Mehr but they are better than the inner senshi

1- the only scout from the future(and past) is Pluto because she guards the time gate
2- they are Mehr powerful(but not surpassing Sailor Moon once she gains the purity chalice) because their job is to protect the entire sol solar system from outside invaders