The 'free' lockers at Universal are quite a bit smaller than they used to be a few years back, and there are NO free lockers near the water rides: JP river Adventure, P &Bluto's Bilge-Rat Barges, and Ripsaw Falls. At those three rides, single-time use lockers start at $4 per locker (if used during the posted wait time for that attraction). The Barges are closed 2/1-2/19, the Falls are closed 2/22-3/19.
At Universal, having to put a bag into a locker and later retrieve it is cumulatively all day adds up to a time drain. In the before times the locker room were also quite crowded, though I imagine Universal has lowered the number of people who can be in the locker rooms at one time. In the before times, using the lockers for the Forbidden Journey and Ginrgott's usually = rubbing up against/being physically bumped by multiple people, especially if it was a busy park day. The area was just that crowded.
At Universal, going bag free is more beneficial than it is at WDW. This is one way the two properties differ significantly. At universal, you see far fewer people with bags, especially big backpacks.
Here's the details: Standard-sized lockers - as in the ones that are free while you ride, are: 14 in x 5.5 in x 16.9 in. The larger lockers are 12 in x 13 in x 16.9 in and cost $2 per use for 'while you ride' duration. Just to clarify, if you leave your stuff in the lockers for more than the allotted ride time, Universal charges more.
One option is to get your wands relatively late in the day, that way you won't have to deal with carrying them around/stowing them in lockers. The wands come in a nice box. It is sturdy, but the less the box is abused, the better, IMO. If you reserve the last few hours of the day purely for wands, then you won't end up stowing the wands much at all.
The wands are pricey, but I think it is well worth getting at least one. Though they sell the idea of each person getting their own wand, sharing a wand works just fine. The spells are very magical, and finding all the locations is fun. The only small caveat is that younger kids tend to need a little extra coaching: the tip of the wand must stay pointed at the windows. Small kids/beginners tend to want to swing the tip of the wand around, rather than keep it level/pointed at the spell area.