No, the standalone version of DCS supports SteamVR without Steam running. You don’t need to use the Steam version of DCS.
You will need to install Steam separately (so as SteamVR is on your system), plus also add the Steam WMR ‘bridge’ bit here I beleive:
There’s a good ‘get started and install’ topic here that should be applicable to the Plus as well:
@Freak did an excellent job of keeping that up-to-date.