I’m using a Fitech 1200 pa and running E20 fuel. What should I set my afr targets?

Depends on what you have your stoichiometric ratio is at.
If you didnt change any of the default settings 12.8-13.1 should be your target value.

My understanding is you can use the same targets it will just take more fuel to get there.

For what's its worth my car is port fuel injected and it doesn't care E0-E10. I don't change the tune and it doesn't change the time slip.

For an emissions test in a lab, stoichiometric ratio is useful. It means that the mixture contains exactly as much oxygen as needed to completely burn every molecule of fuel: no more, no less. The result is water and carbon dioxide only.
This is not what a car engine does (completely burn fuel, supra), and that number is not optimum for any particular RPM, vacuum, throttle position, spark position, or power level. Best WOT is always richer than stoich, cruising is leaner, it should vary throughout the range depending on conditions.

Should I increase cubic inches by 5-7% to increase fuel like when using e85?