I have used 87 with an octane booster that is cheaper than paying for 91 or especially 93 but not sure how accurate their advertised boost might be! I have tried this and have not experienced any knock so should be good if you are not stomping on the gas!
I change my oil on the ‘21 CTR when my onboard computer says 10% service life left. I just did the third oil/filter change and my car with only has 6500 total miles. I’m not sure why so often with so few miles?