We’ve been to Universal three times in the past year. Depending on where you want to eat, yes, make reservations. It used to be you could pretty much walk up and get a table, but dining has been hectic and people were absolutely turned away while we waited for our reserved tables, so don’t trust that.
That said, you should be able to make reservations much closer to your actual trip. It’s not as ridiculous as Disney.
Some recommendations:
Islands of Adventure. For table service, we’ve done both Mythos and Confisco Grill. Both recommended by us. Mythos is overhyped in our opinion, but I can’t deny that it’s very good. For quick service… look, I love Harry Potter. The Three Broomsticks is… ok. Every time we’ve eaten there (even pre-covid) has been chaotic, in a negative way. I’m sure they’re better now, but back last March we waited something like 30 minutes to sit, then another hour to get our food, despite having mobile order. It may be better now. Get more recent opinions. On the flip side, Thunder Falls Terrace in Jurassic Park was fantastic and easy, and has some of the same food as The Three Broomsticks.
In Universal Studios, we’ve done table service at Lombard’s, which was pretty good and very relaxing. We’ve had less issues with the Leaky Cauldron compared to Three Broomsticks, but it can still be chaotic.
CityWalk has a TON of options. We’ve never done Toothsome, but if that’s something you’re interested in, definitely make a reservation- we’ve seen lines extended down the walkway pretty much every time we’ve been by. The Bob Marley place doesn’t get as much credit as it should, so I’m going to recommend that.
And don’t discount resort options. Where are you staying? We’re Cabana Bay regulars, and honestly the food court is pretty dang good. We always get food from there or The Hideaway (pool bar and grille) a few times each trip and we’ve never been disappointed.