Hello,
My experiences are with LV-DSC 6.1 (& earlier) from a couple of years ago. We used Modicon and AB PLCs on different projects with 1200 - 2000 PLC IO points.
Imo, 1000 IO points is a LOT for data sockets. If the OPC server is fast enough, the data socket server *might* keep up, but the CPU load would probably be pretty high. The 6.1 DSC engine was fast enough & quite efficient (for "memory tags"), but its the OPC server & the PLC(s) that may not be fast enough.
Test EVERY OPC server available (PLC vendor's, PLC-interface card vendor's, NI's, & 3rd-party like Matrik