Inogen makes and sells back packs for their unit. It is important not to block the intake or output of the unit for proper use and not over heating.

I sometimes put the shoulder strap over my head to keep it from slipping. But prefer the shoulder. As far as your cannula, just over the ears, in the nose and since it up under the chin. I prefer soft ones. The more you use it you will get used to it.

Not sure what mine is but when using the backpack or the caring case it gets hot

Hot? Yikes. That would smart!

I need to pay better attention. I have an Inogen G3, NOT a G5.