I have, from what I can tell and confidently say, definitely seen a big difference, especially in the speed of launching a SteamVR game vs launching a SteamVR game with Oculus running in the background. And its not a problem I usually have, SSDs, i7, NV 1080, 16GB ram, I mean I don't have a problem launching stuff so when I say it makes a difference I would imagine for a pc with the same or less of my pc there would be a noticable difference too.
And as for performance, I could not tell any difference, besides negatively, of running with Oculus vs without in terms of graphical and experience, except the bad one of having multiple virtual reality programs running simultaneously.
Oculus tray tool has an option to set ASW mode, but really it boils down to....
The easy way to make it so Oculus Home does NOT start when you want to run SteamVR is to right click the Oculus shortcut on your desktop, choose "properties" then choose the "compatibility" tab, then click the "run this program as an administrator". To run Oculus Home once you have done this, you have to double click the desktop shortcut. 🙂
I just did this, clicked on the oculus short cut in my start menu, set it to administrator, then fired up SteamVR but Oculus Home opened anyway.
I also tried doing this directly on the oculus client file here: C:\Program Files\Oculus\Support\oculus-client and it made no difference, oculus home still launches with SteamVR.