So, once you create a mint with a transfer fee, you can't update the fee later?

As far as I understand, it is possible to make custom transaction instructions with @solana/web3. I think I can implement this functionality, but I need help finding out what transactions are being sent when deploying a program and their payload schema.

Actually, I plan to keep the program upgradable since I'm planning to add more features in the future.

I'm trying to keep my whole workflow around TypeScript and have my own set of functions to interact with Solana network. Using CLI isn't reliable in my case since I won't have full flexibility especially when it's about key management.