That's what I get for being fast and loose with my terminology
No, if you wanted upsampling you would just upsample, and it looks like you have to do this offline first if you want to do this together with DRX10K, yes (to answer your last question).
The "oversampling" regarding my plugin actually refers to analyzing and processing "overlapped" windows of sample data, to improve its time resolution. If e.g. the plugin looks at say 1024 samples per frame, the usually accepted maximum distance one jumps for the next set of samples is 512 samples, or half the window size. This is what is done at 768kHz. At say 48kHz, it only needs to look at say 64 sample windows, to cover the same amount of time per window (becaise sample rate), and for this it can afford to only take 1/8 window size hops per processing step, in this example 8 samples. Taking hops 1/4 the nominal accepted distance is what I referred to as "4x oversampling" and this is more important for the algorithm than actual upsampling, because while the analysis windows are nominally say 1024 samples wide, you "see" more clearly out these "windows" in the middle of each window, so it is good to catch each drum hit etc. in the middle of one such window to yield the desired processing and not introduce any unwanted distortions.
Phew...