ARD and Screen Sharing use the same protocol and the same client in macOS. Any performance differences between the two will be negligible at best.
Test the performance and latency of the connection, and see if that matches your expectations.
You likely have a network limitation or network problem, you’re not getting the bandwdith or the latency that you expect, or there’s some other issue lurking somewhere in the client kr server or intervening connection that’s effecting the performance.
Screen sharing does take a fair amount of bandwidth, and ssh or similar works better for some tasks and particularly on lower-performing links.