I have some heavy hashrate boost on my 4 GB devices using Rave OS and 1.21.

12:47:42 Average speed (30s): 16.78mh/s | 25.48mh/s Total: 42.26 mh/s

#1 is in the 1st 16x slot and #0 is in the 2nd. There is third GTX, but using different miner.