My best rates for a single card.

Vega 56 drivers 18.8.1 - XMR-Stak - Windows 10 - XMR - Monero CNv7
OC with power play tables and overdriveNTool
Mem 1100
Clock 950
Temp - 55-60c - ambient room temp doesn't help 65-70f
No killowat meter to test power draw , yet.

10s - 1920/hs
60s - 1940/hs
15m - 1950/hs

Results
2141/2141 accepted shares - No Rejects!

My AMD.txt
"gpu_threads_conf" : [
  // gpu: gfx900 memory:3920
  // compute units: 56
  { "index" : 0, "intensity" : 1932, "worksize" : 8, "affine_to_cpu" : 0, "strided_index" : true, "mem_chunk" : 2, "comp_mode" : false },
  { "index" : 0, "intensity" : 1932, "worksize" : 8, "affine_to_cpu" : 0, "strided_index" : true, "mem_chunk" : 2, "comp_mode" : false },
],

Running stable for the past week or so at this rate with no hashrate drops

https://imgur.com/a/WeHNhGX

Happy Mining!

TheMiniMiner