If I remember correctly, the ranked events without website are sometimes recognizable by Chopperman Missions that say "get X points playing Y quest to get reward Z". To be always safe, the first time you play a new island don't use 1 wave: at the Rewards screen after you win there will be a "Points" section right under the info of berries and exp earned during the quest like in the attachment.
I guess that dmg multiplier is a preference, I guess that 10x could be enough for most of the content. I probably exaggerate using 500x (never had problems btw) but I do to be sure to complete a quest using the auto button also if the enemy has a very high defense/damage reduction or gives me atk down/unfavourable orbs/despair and other effects that lower my potential attack force.
TL;DR: Use a multiplier you prefer and be careful playing islands, do a run just to see at the end if you get points.
ONE PIECE TC 
