We go in the "back way" on local roads, from where we live in Middleburg (right off of Orange Park/Fleming Island, FL). Still a toll road, and it's definitely back there, but much much better than I4. It takes us about the same amount of time during nonpeak hours.. I've seen logging trucks and construction equipment running on these roads, so I think an RV should be ok, but don't quote me.
From I295:
Exit onto US17S
US 17S through Green Cove Springs
Keep right to US441S/Apopka/Orlando (then go 13.65 mi)
Turn left then keep to the rights to SR 429E/SR 414E
Keep left SR 429S
Keep right Exit 8: Disney World/Hartzog Blvd
After 823.49 ft, keep left to WDW