What’s strange is that Snapdragon 835 and 820/821 all kinda cluster around a very wide range of 1900 - 1500 in Geekbench 4. The results are ALL over the map, with the OnePlus 5 with the newer Snapdragon 835 down around 1685 for no reason I can discern, and while the LeEco Le Pro3 is way up at 1813 with an older Snapdragon 821.
So TL;DR yeah performance is a complete crapshoot on Qualcomm currently with their last 2 chipsets (821 and 835).
However below that upgrading is a bit safer?
Once you get to the Snapdragon 650, you are looking at ~1370 or below
Once you get to the Snapdragon 810, you are looking at ~1250 or below
I guess if you went from an 810 or 650 to a high ranking 835 That wouldn’t be too bad … 1250 → 1800 is 1.4×