My I:C ratio varies from 1:8 to 1:14 depending on activity level and hormones. Activity level definitely has a huge effect, and a huge effect on basal rates, too.
Currently I’m at 1:10 for all meals. I hadn’t thought of changing it for different meals throughout the day, but may do that. For a while when I started pumping I used a slightly higher ratio at breakfast, and I may have to go back to doing that as by far breakfast is my hardest after-meal blood sugar to control.