For instance if any EA titles will no doubt be either retail or origin versions. (unless older titles where it will be on steam also)
Other titles use Retail and Steam as mediums.
Its very rare that people get from onlive on a huge scale compared to steam. The only thing you can do is try it and see.
Hope that answers your Question.
It seems as though every bit of data(save games,data files, etc.) for the games from Onlive are stored on their own servers in a cloud-like system, so trainer applications on you pc would not be able to effect the game(s) without direct cooperation from Onlive. in short, no. or rather, not right now anyway.
here is a Link to the full article.
[Edited by moderator dstates, 10/29/2012 4:53:07 AM]