Hiya,
I always go to DRLP low-season (ie term time, midweek).
I don't do queues

. The big rides will have lines - but nothing excessive (and a lot of them have fastpass).
Fantasyland does get busy from late morning onwards, so if you have little kids it really is worth doing EMH if you can, as most of the rides in Fantasyland are open druing EMH. Dumbo in particular quickly builds up queues (but if you can't get on Dumbo, Flying Carpets in the Studios is a very similar ride, and usually is a walk-on). IASW is usually a walk-on in low season, as is POC.
I'd say, just going from past experience of early October in 15th anniversary year, if you see a queue line showing more than 20 minutes, just come back and try again some other time in your visit.
If you want to do the queued meet and greets in the park, you may have to wait a bit longer - we waited about 45 minutes for one of the Princesses, but only because we wanted a specific one (we could have met Cinderella within about 15 minutes).
Elaine