I've had the two Octos running around 30-50% in a 4X2X2 tank, one on the right and one in the back on the left for flow behind the rocks on the left. I also have a XF 350 cloud on the left opposite the right OCTO4, again running no more than 50%. All are on a Hydros wave-engine SPS mode, FWIW. Water movement is great.
Correct me if I'm wrong, but I believe heat causes precipitation which can cause a pump to freeze - had this happen in my previous tank with an AC pump that failed and I lost livestock, with a LOT of deposit around the impeller very quickly (had a Ca reactor). Now I run all critical pumps (DC) less than 50% and clean them in citric acid every couple of months (that reminds me...). I also feel the lifespan would be longer if not run at full speed.
I am not sure that a pair of OCTO2s are enough for robust flow. FWIW, I have a SICCE XSTREAM (up to 2250 mph, comparing to OP2) behind rocks on the right. While it provides good flow, I don't think a pair of those would be sufficient for primary flow in the tank, perhaps unless run closer to 100%.