While there is no required buffer, your account still operates under the standard 3% Overall Drawdown limit and since there is no system-imposed buffer holding balance back, you are responsible for managing your own safety margin.
On a $20,000 account for example, your Overall Drawdown stop-out is fixed at $19,400 ($20,000 minus 3%, which is $600). There is nothing preventing you from requesting your full available profit down to the 1% eligibility threshold, but if you do, you are trading with very little room before a breach.
Example ($20,000 account): Initial Balance: $20,000. Stop-out limit: $19,400 (fixed, does not move until first approved reward). Minimum balance to request: $20,200 (1% above initial).
If you request your full profit at $20,200, your remaining balance is $20,000 which is just $600 above stop-out.
After your first approved reward, the Overall Drawdown stop-out moves permanently to $20,000 (your Initial Balance). From that point, any drawdown that brings your balance or equity to $20,000 results in a breach including from full payout requests.
There is no rule requiring you to leave a buffer but leaving one is strongly advisable. How much you keep as a personal safety margin is your decision to make as part of your risk management.