Hallways are tight, especially the stateroom hallways. People who leave things in the hall make that even more difficult. Housekeeping carts can be moved easily, if you don't see a stateroom host they are in a room near the cart so maybe call out. Other items like strollers or
ECVs left in the hall are annoying because it causes a challenge.
Some doors, particularly doors to the outside decks, can be hard to pull open while on an ECV.
If you/your family member will need to use the ECV in the main dining rooms, I suggest having your reservation noted for that, and also check with "dining changes" the first afternoon to make sure it will be accessible. Otherwise some of the pathways through the dining rooms are tight between tables.
At the shows in the Walt Disney Theater, you should be able to arrive early and be taken in a side door for accessible seating areas. Arrive a little extra early the first night and ask the CM.
It's good you have an HA room booked! Regular stateroom doorways are usually not wide enough for most ECVs to enter.
Are you looking for excursions? Depending on destination those can be hard to find something accessible.