We are about to leave Iceland and had an enjoyable 3 nights. After being in warm Stockholm, the weather in Iceland was a welcome relief (50s F). We stayed in an airbnb which was in Reykjavik but away from the touristy town center.
We used the tour company, Nice Travel for a Golden Circle minibus tour. Loved the tour. Our driver timed our lunch stop so we could eat when it was less crowded. He also stopped at extra stops (Icelandic horses, extra waterfall, farm where we could get ice cream, lake in a crater) in addition to the big three sites. He dropped us off where we requested in Reykjavik so we could visit the Saga museum.
We skipped the Blue Lagoon for a local pool, Vesturbæjarlaug. What a relaxing experience! We especially loved the shallow heated pool where we could lay down flat and be completely immersed with our heads resting on the pool edge. The pools are used to tourists so will give you a briefing on the showering rules (plus they are spelled out in Rick Steves Iceland).
One of our favorite restaurants with local Icelandic foods was Kafe Loki which was right across from the church, Hallgrimskirkja. Highly recommended the fish of the day. It seems that a lot of restaurants have additional seating upstairs so don't be turned off when a restaurant appears to be full when you look in the window.
We enjoyed the National Museum of Iceland, The Settlement Exhibition, and Hallgrimskirkja. We walked along the waterfront near our airbnb as well as exploring the town of Reykjavik (we got around on foot our entire time in Reykjavik). Lots and lots of public art to see (even in people's yards).