Hi bluejasmine!
CR fan already addressed your questions, but I just wanted to add our favorite fun way from BC to MK and back - the monorail!
It may not be the fastest route and it won't work if you don't have park hoppers, when you want to get to MK before Epcot opens or when you leave MK after Epcot closes. Under those circumstances, the only Disney transportation is the bus. I know that Dee (natebenma) has additional information from her family's races, so she can comment on the timing.
If you have park hoppers and you're going to MK after Epcot opens or coming back before Epcot closes, the monorail is a fun alternative! From BC to MK, we walk through the Epcot International Gateway, grab a snack (or a slushie in France), maybe do a Kim Possible mission and make our way to the monorail. And sometimes we just walk straight through. From MK to BC, if MK closes before Epcot (especially when Epcot has evening EMH) we love taking the monorail. We can catch Illuminations, grab a dessert or snack and walk right out the International Gateway to our BC room. Again, it may not be the fastest but it's more festive than the bus!