First I want to say that Peter Pan is only good for Rope Drop if you can be on within 10 minutes. Otherwise it is better to go another time. Using 20 minutes of prime morning time to wait for that ride isn't worth it as you could likely ride 4-5 other rides in that time.
Winnie the Pooh rarely has a line. In regards to why, it is likely partly because it is in the back of the park as others said. But also it has a "higher capacity." That is all of the Fantaslyand rides only hold one family (or half a family). But Winnie the Pooh can hold up to three separate families. I don't know if the ride can actually ride more people per hour, but I am sure that helps the line move a bit faster.
Alice and Mr. Toad can have longer lines. Alice has always been popular, and since it was revamped a year ago it's been even more popular. It's a fun ride. Pinocchio and Snow White are considered "scary" rides for little kids and the lines are often shorter. They also both easily hold a family of 4 or even 5, where as Peter Pan and Mr. Toad do not.
Touring Plans lets you look at average wait times for rides by hours of the day for free.
https://touringplans.com/disneyland/wait-times