" On any slight up hill inclines where I couldn't peddle as fast I shifted to 6, even though normally I would've stayed in 7. I didn't really feel any kind of improvement. It felt like I was going faster in 7. This is why I originally wanted a bike with higher gear range, it seems I can go faster at higher gears, even if I'm peddling slower. I am not yet a believer in this high RPM "spinning" concept, but I am a newb and if the pros do it, I will just have to adjust, maybe it will come to me once I cycle more..."
It's relative. If you're spinning out, you're spinning out. If you have the strength and fitness to go for more gear inches, then that's what you need. It's what's comfortable for you. Try another bike. Eschew dogma!
Regarding sidewalk cycling, I believe that's also relative. I cycle on sidewalks in the UK when it's just too dangerous for me to be on the road. With traffic passing me at 70 mph on major roads, I'll always take the safe option. In the UK various police forces differ whether it's allowed. In rural Oxfordshire, it's very common, in London, you'll get pulled.