I believe memory overclock is the least taxing in relation to battery and thermals. If your plan is to just overclock the memory and leave the CPU and GPU at stock frequencies, it will be just fine for handhand and docked modes.
I have my Erista with Samsung memory overclocked to 1996.8. Mine tops out at around 57c (ambient temp around 75f in my room) with 1224/921 CPU/GPU in docked mode for BOTW. I recently cleaned up and replaced the thermal paste in my v1, though.