Arena matchmaking is based on your trophy score, you will get matched up against a player with a trophy ranking close to yours. Sometimes this will, unfortunately, mean that the opponent's team might be stronger than yours, sometimes they will be weaker.

Matchmaking for scouted markers functions a little differently in comparison to regular Arena, as the scouted matches are balanced according to your team power. Please keep in mind that winning or losing a match via scouted marker does not provide nor deducts your trophies.