Most all ride lines can accommodate a wheelchair. ECV users have the option of parking and walking through the line or transferring to a wheelchair for the ride line. Wheelchairs are provided for each attraction. Just ask the attendant.
Some rides can accommodate a wheelchair on the actual ride. They do not allow ECVs on any rides.
Islands of Adventure has a fully detailed Rider’s Guide for Rider Safety and Guests with Disabilities available on line here: https://www.universalorlando.com/Images/Riders_Guide_tcm13-26195.pdf