So, using this profile, I get a bunch of flickering everyhwere (running 2x GTX 1080).
I have also created a profile that, in my testing, offers the same performance. It's based on the GTA 5 profile, but I changed Anti-Aliasing compatibility (weirdly with subjectively better results than changing them in Sajin's profile, more testing would be necessary to examine that, but since the performance is the same, I'm not very motivated).
In the benchmark (I actually haven't done any gameplay testing yet), in the first scene, the trees still flicker, but nothing else, in the second scene, it flickers while it fades in, but then, it runs through the rest of the benchmark without any flickering and with decent performance.
In case you want to try this profile, here it is:
 
Profile "RDR2 Custom" UserSpecified=true
ShowOn All
ProfileType Application
Executable "rdr2.exe"
Executable "red2.exe"
Setting ID_0x000858f7 = 0x00000001 UserSpecified=true
Setting ID_0x00a06946 = 0x0a0040f5 UserSpecified=true
Setting ID_0x00d55f7d = 0x00000240 UserSpecified=true
Setting ID_0x10115c8b = 0x0000003c UserSpecified=true
Setting ID_0x1033cec2 = 0x00000002 UserSpecified=true
Setting ID_0x1033dcd3 = 0x00000004 UserSpecified=true
Setting ID_0x10ecdb82 = 0x00100001 UserSpecified=true
Setting ID_0x10f9dc81 = 0x00000011 UserSpecified=true
Setting ID_0x701eb457 = 0x00000001 UserSpecified=true
Setting ID_0x708db8c5 = 0x40000000 UserSpecified=true
Setting ID_0x80857a28 = 0x00000001 UserSpecified=true
EndProfile
 
Obviously, you can change the name, and I honestly don't know why the "UserSpecified=true" is behind the name, if you want to, you can remove it. You can also change it to "ShowOn GeForce", I did neither of those changes manually, but they also haven't made a difference, so I didn't change them back.
It also doesn't matter if the "red2.exe" is added at the top, at least not for the benchmark. I left it in becuase maybe it will be relevant during gameplay, but I doubt it.
 
You will need to remove the Executables from the "Red Dead Redemption II" entry, and change the ProfileType to "Global" (or delete the entire entry).
 
The important line is "Setting ID_0x00d55f7d = 0x00000240 UserSpecified=true", this is what changes the Anti-Aliasing compatibility to the Assassin's Creed setting, which actually makes sense as those are also the Sli settings that the profile uses (the Sli bits are officially suited for AC and GTA 5)