I don't recommend the inside sites in the north loop - sites are super duper close together with only sparse trees in between. It was a noisy night with dogs from a couple different sites barking back and forth at each other into the wee hours, and my campsite neighbors getting in late and bickering as they set up their tent, their headlights facing my tent.
The map was misleading as to the location of the toilets. I don't like to be immediately adjacent to the bathrooms, and I picked site 97 with this in mind. Unfortunately, there were two buildings with vault toilets (only one indicated on map), one of which I'd estimate was under 50 feet from my tent pad. Luckily, smell wasn't an issue, but it did mean a lot of foot traffic nearby.
The park itself was nice - lovely view of the water from the trails, maps at most trail intersections and the trails were not too busy.
We had to wait over an hour for a site to be vacated at this campground (I suspect this was partially related to a lot of Mazama being closed), but our persistence paid off and we were able to put our tag on site 3 as the previous occupant was packing up.
Upsides: inside the park, convenient starting point to go on a boat tour the next morning, good hammock trees at site, quiet (we hardly heard or saw any of the other campers), cheap!!
Downsides: not a lot of shade, no water at the campground unless you filter from the creek, bathroom building is closed (but the Porta-Potties were clean), lots of mosquitos
We had a reservation for the night at Mazama, which NPS cancelled <24 hours prior to our arrival so we were left scrambling for another place to stay. This campground was on the list of outside-of-the-park alternatives, and we were able to grab a site (one of several that were available) when we arrived around 6pm. The campsite was nice and right along the creek, the water tasted great, and it's relatively close to Crater Lake.
This is a really nice park and I love that all the campsites were backcountry sites so it was nice and quiet and secluded. I took the slightly longer way to my campsite, but going the shortest route would have been under 2 miles. There are lots of trails in the park, which is mostly flat - I hiked ~15 miles the second day I was there. It was a bit cold in May to hang out on the beach, and I did build a fire each night for warmth. Highly recommend visiting during a new moon if possible - there are SO many stars. There was shore access from my campsite so I could filter water for cooking, etc. There is also potable water at the ranger station as well as flush toilets that are open even when the ranger office is closed.
I was looking for a campground open in March to try to see the aurora (unsuccessful due to lack of auroral activity) and Point Beach fit the bill. Only a couple loops in the campground were open for winter, including sites 1-20 which are non-reservable year-round. These sites are close to the picnic area near the beach and lighthouse. Every site except the one I stayed at were still mostly snow-covered in late March. There was only one other group of campers the night I went, so it was nice, quiet and secluded. I imagine in warmer seasons it's a much more crowded, noisy campground.
I backpacked the IAT with a group and we camped for the night at Mauthe Lake at the beginning of April. There are lots of downed trees at the campground, which sort of detracted from the landscape (tornado damage, I'm told). Pit toilets were open, but water had not yet been turned on so be prepared to filter if you go this early in the season. We perused different sites/loops for a while to find adjacent non-electric sites large enough for multiple tents at each and were able to fit 8-9 (small backpacking) tents between 314 and 313.
Each site at the cart-in campground was secluded from view from the others. Mine was right along the water with a path down to a small beach and rock outcrop, nice for sitting and watching the water. The one downside was that the road is so close you can hear cars going by at night. Traffic is fairly light in the evening so it's not too bad, but it did detract some from the ambience. This campground did not connect directly to the rest of the trails - it was a 10 minute walk or so to get to the main trails.
Drinking water had already been turned off for the season, but the bathroom still had running water and flush toilets in mid-October. Easy access to hiking trails. My site was close in distance to adjacent ones, but was on the edge by the creek, so it was pretty quiet. None of the cart-in sites were vacant the night I stayed, but those looked lovely as well.