I would go with 140°F/60°C for 2 hours for medium lamb chops.
It is safe to eat meat that has been cooked to the proper temperature/time profile without searing. Searing adds flavor and improves the appearance of the meat. I often cook pork tenderloin and use it on salads with a very light sear.
Don’t be afraid of searing. Using a hot pan and a bit of oil it will brown up nicely. Remember to use a paper towel to dry the meat first to get a better coating. When I started overcooking was a concern I had that turned out not to be an issue.