Yes that hose is plastic. My inlet hose is metallic. Should i change that one to plastic as well?

I'm ok with the position. Maybe I'm a small person.

Can you eloborate more on why do you think that it's unnecessary to change to a plastic hose? Don't you think it's dangerous to have a metallic hose at the inlet in the event of short circuit?

How about accidental contact?

What i usually see are the shower head at most reach to the mid point of the water heater unit, while in your case the shower head can go above, and that mean possibility of water from the shower head plash to the unit if it was adjust to the highest point.  I usually install mine with the temperature knob and the power on/off are reachable while the top part will be higher and shower head won't reach the top.