If you really want to do this right. Set up an excel spreadsheet and lay out the ratios with gear inches and cadence.

You can use columns for inner and outer rings, ratio, GI, etc; and rows for cassette cogs.

Then based on your current routes and gear combinations used, you’ll be able to compare current to potential.

I’m all for setting up your bike how you want it, but a lot of people over-estimate the effect of 1 or 2 teeth.

But I agree that 11-13 is a horrible gap. I’m not familiar with 12 speeds, but can’t imagine any 12 speed cassette with that gap.

John