All sites are reservable and are pretty much snapped up at the six-month reservation window but we showed up in mid-August and were able to snag a couple of sites released by folks not showing up for their reservations. The 1-16 loop has the best sites for access to your car and proximity to the lake. Odd numbered sites 9-17 also have no backyard neighbors and more privacy.
Lake is very swimmable but no motorized craft allowed. Cool section of river channels at the back of the lake toward the Twin Lakes Trailhead.
Twin Lakes Trailhead takes you to desolation wilderness and some great day hikes. If you're in decent shape you can easily do the Twin Lakes/Boomerang/Island Lake trail, but pack a rain jacket for surprise alpine thunderstorms. These Lakes are colder but still pretty swimmable. Absolutely beautiful.
Be prepared for lots of mosquitos early in the season. They were mostly gone by mid-August, but I sustained a few munches when I was there in early July.