I'm wondering, when it ends, whether to rewatch it first, or move on immediately to Legend of Korra, which I gather is somewhat less admired by audiences, but don't know anything about except the one thing.

FWIW, I'm watching it on Paramount+, which I have for Star Trek. Happily, AtLA -- and maybe all the kids stuff? -- has no commercials in it, even though I'm in the must-watch-commercials subscription tier and get them in the adult programming.