We just came back from a week with a big emphasis on characters for my 2 yo. MK and Epcot we had the best luck with actual characters. In Epcot we waited in Norway twice and maybe we got lucky but within 10 min, once Elsa walked out and later in the afternoon Anna did. Also saw Joy out twice by the imagination lawn.
In MK we hung out on Main Street by Tony’s and saw characters up on the train balcony probably every 15-30 minutes and when they came out they’d be out for about 10 minutes at a time. Saw the princesses multiple times (rotation of which ones were up there), Mickey and friends multiple times, Winnie and friends also multiple times. Saw the characters in the MK calvacade once up there (Peter Pan, Moana and others). For calvacades you can also watch from Main Street. The times listed in the app are when the first one starts in Frontierland so if you’re on Main Street add 10-15 min to when the first should appear. The last time listed in the app is typically the actual last one also.