i have a mixed rig with rx570 and gtx1070 in it strap 1 gives 1070 2.5mh; rxboost 1 gives rxs 0.5 mh if i run them in 1 copy of claymore rxs dont get this 0.5mh from rxboost if i run 2 copies of claymore 1 copy cant use straps due to driver is already in use.
I have one mixed RX580 & GTX 1070 RIG - In the start.bat I use: "-strap 1 -sintensity 20 -rxboost 1"
Not sure if you have your string setup like this or not; but I gained 50 Mh/s across the Rig overall.
Hope this helps
Peace,
WX2