There is no such thing as an "SR+ Medium Range". There is a "Mid Range", (a.k.a., LEMR - Limited Edition Mid Range) which was produced for about 5 months from ~Oct 2018 - Feb 2019. it has the same pack as the LR with some cells removed. This was a temporary measure to offer a lower cost car because the SR/SR+ design wasn't complete yet. The Mid-Range has the full "Premium Interior" that the LR models have.
The SR is the exact same car as the SR+ (including pack) with the SR being software locked to lower usable capacity and other features.