My point is even 5th year seniors make those mistakes. Every Qb needs to learn how to adjust to reads and make the right throw. It takes most 4 to 5 years to get where Tanner was last year as a freshman. So yes I believe Tanner will be better than Taysom at every aspect except making plays with his feet next year.
It makes sense to keep Taysom on the team for depth as a fan perspective. But that might not be what is best for him. If he stays and Ty decides to make Taysom the starter then great. I personally think Tanner will be the starter regardless.
The best case scenario in my mind is start Tanner and figure out a way to implement Taysom in and give him touches. But again that's not what is best for Taysom.