Most banks have a fixed monthly payment in the 0% interest period based on percentage of the current balance (1% of total balance for Chase, 5% First Citizens, etc).
Amex is the only one where the percentage varies based on the balance amount. This is the breakdown:
1% of balance due for balances $0-$20,000
2% of balance for $20,000.01-$35,000
5% of balance for $35,000.01-$50,000
10% of balance for $50,000+
Good to keep in mind when choosing amounts to liquidate - $35k or $50k rather than $36k or $51k for example. Hope this is helpful!