Pressure is indicated by bike manufacturer, not tire company.
Nitrogen is used for consistent pressure through varying temperature.
Your tires won't pop if you run 50 psi in them.
Pressure is contact patch and retention of shape.
Some AMA road racers use low 20s on pressure, which shocks me... but they tune it with suspension (and often use nitrogen AFAIK
I tried, but was unable to prove difference in tire life between running 44 rear, and 36 rear. Theory would dictate, smaller contact patch would wear more slowly... but then you're using a smaller portion of the tire with all of the weight of the bike. Soooo... I just run manufacturer spec.
At the track, I never go as low as the coaches recommend. There I usually run 33 and 33.
Every licenced racer I know uses high 20s at the track. Why don't I? I don't know.
Can't tell you about difference in fuel economy at different pressures... I'm just thrilled that on a bike I get about 3x the fuel mileage of my truck.
- on bikini patrol in FL