Acavia wrote:What does "45" mean?

That's the grind setting of the niche. The niche is stepless but the adjusting ring has numbers on it for reference

This has always confused me because I find water off the boil to be far better in most cases. Not only does it taste better to me, it also drains faster allowing for a finer grind. Could it be the water profile, aside from taste preference, that leads to different experiences? My tap water is very soft:

Ca 25 Na 12 Mg 4 SO4 39 Cl 13.5 HCO3 59 pH 8.5

..perhaps leading to inefficient extraction at lower temperatures.

I agree with you that softer water goes together with higher temperatures. Besides water quality, I've found that higher temps doing better in a V60 also correlates with lighter roasts and better greens.

Acavia, That's the Niche setting used on that PO

I also have moved around to a wide range of temperatures, and have had enjoyable but different results (perhaps only due to not compensating by adjusting other variables) at both ends of the spectrum. I'm very curious about patterns other people are finding in these regards.
However I feel I could learn more from these discussions if slurry temperature is discussed rather than water temperature. For what could be a small list of reasons, the same water temperature will yield different slurry temps based on the timings of my pours. When I was brewing (in v60) with a bloom and two pulses, my slurry temps would peak (and sink) more than when I brew with a bloom and 4 pulses