Universal isn't Disney so my main point of advice is not to treat it as such. Stick Royal Pacific Resort, Portofino Bay or The Hard Rock Hotel as unlimited express passes are built into the pricing for the room.
You don't need ADR's as everything is first come first serve, but will get preferred seating for staying on site. No clue about the dining plan as I would never get one at US or WDW.
I wouldn't book a package unless your trying to pay everything off before the trip. You can buy a park ticket at the gate and would have no bearing on what rides you could or couldn't get on as you would already have express pass from staying at one of the 3 deluxe hotels (Cabana Bay Beach Resort, Sapphire Falls & Adventura do not offer unlimited express passes as a perk for staying). Also depending on how long you are there Annual Passes may be a better value plus you would get a discount on the room.
The three deluxe resorts + Sapphire Falls has a boat that will take you too and from the parks dropping you off pretty much in the middle of the two entrances for Universal Studios and Islands of Adventure. . Cabanna Bay and Sapphire Falls have bus transportation just like Disney. There is no magical express from the airport, best bet is an Uber.
Another perk of staying on site (This goes for ALL 6 hotels) is early access an hour before the park opens. Each day it varies what park so that you would need to check the site for.
If you have an unlimited express pass and plan on doing just Islands of Adventure and Universal Studios (This is excluding their water park Volcano Bay) you can get that done in 2 days maximum. I would suggest a 3rd day to do any repeats or if a ride has a closure for some reason.
I never do Disney without going to Universal and vice versa but i treat them as two separate experiences. At Disney I know that i need to figure out what i want for dinner 6 months in advance, at Universal i can be relaxed and decide on the fly.