what do you mean by an instrument track? Reaper doesn't really have specific instrument tracks.
Set up a track template with the plugins you want & load that.
Sorry the way I have Reaper set up is you have tracks set up either for Midi or a instruments. To be clearer I would like to load all tracks a with a gain plug and a scope already preloaded. I am presuming with a temple I would have to have a loads of tracks already set up. Would like to do it one at a time as I need them.
set up a track with your gain & scope
save as a template
then every time you want to load a new track, load this template (you could assign it a shortcut or an icon on a toolbar or whatever)
Pre load plugin on a track.
Linear Mode
