As for SPG, I haven't heard of it used in any loading, over 1500 fps. It's used a lot in BP loading but, in Schuetzen matches (1400 - 1600 fps), it's not used that often.
Regarding Darr Lube(50/50 Vas/paraffin), I used it for 10 years. It wonderful, under 1500 fps and under 85 deg (leads horribly at 100 deg). I had to keep my lubed bullets in a small ice chest at above 80. It does not work at >1900 fps, because it wasn't accurate.
I tried Vas/BW, also but at this late date, I don't remember why I didn't use it at 1900+ but, if it showed good results, I would have remembered.
The only lube (home brew types) that worked above 1900 fps was lith/BW. I first tried it 50/50 but, it was way to tin, for my liking so, I cut it to 30% and it worked well and produced good GC groups up to 2250 fps.
I think a good, all round lube is 50/50 BW/alox or the original NRA formula.It works to 2000 fps or more. I now use 25/75 BW/ alox and will increase the BW to 30% later, to stiffen it a little. I've shot extremely good groups and scores, with it but, I don't shoot at 2000 fps.