Clan war matchmaking is based on the strength of the members. Not their level. You can have a level 100 player that is much weaker than a level 50 player because the level 100 player just likes to chop trees down more.
LOL. Give me a screenshot. I have never seen a lvl100 player that can be weaker than a lvl50 in any way. Dont' post ♥♥ here just to prove your point.