I would assume so. That's interesting that it's quieter at full speed. I'll crank mine up next week and see if I get the same result. Tank is cycling at the moment and the S2 is only running 20% for the reactors, so can't mess with it at the moment.
Dunno! I run my vortechs up to 100% and some of them are 7 years young. Always amuses me when folks put 'only ran at 50%' or 'barely used' in their for sale adds. Do they think that means people will pay more? I was born at night ..... just not last night!