Honestly, most IPTV Reseller Panel platforms advertise an API. Few tell you the rate limits before you buy. I've seen a reseller build an entire automation system around a panel's API, only to discover he could only create 10 accounts per minute. He needed 200. His British IPTV promotion went viral. His panel choked. New customers saw errors. They went elsewhere. The panel's fine print said "100 requests per hour." He missed it. Expensive miss.
What actually works is testing the API before you trust it. Write a simple script that creates British IPTV test accounts repeatedly. How fast can you go before the panel starts rejecting requests? One reseller I know ran this test and discovered his panel's undocumented limit was 30 accounts per minute—half of what he needed. He negotiated a higher limit before signing. His current IPTV Reseller Panel published its limits clearly on the pricing page. No surprises. That said, most resellers never touch the API. If you plan to grow, you will. Ask for the rate limit documentation before you ask for price. A transparent panel provides both.