You have to edit the local config file (local.conf). Check this out:

http://ethosdistro.com/pool.txt

I only use AMD gpus in the rig that runs Ethos, so I have set it as follows:

maxgputemp 80
globalfan 50
globalmem 2150
globalcore 1150
pwr rigname 3 3 3 3 3
vlt rigname 850 850 850 850 850

You have to look for optimal settings for your Nvidias, I guess it won't be difficult to Google them.
On Windows, I use a 65% power limit for 1070s.