The orifice meter has a higher head loss than the venturi meter for the same flow conditions.

The bend causes a larger head loss than the orifice in low flow conditions.

The headlosses through the venturi meter are mostly due to the manometer tappings.

The venturi meter has a higher head loss than the orifice meter for the same flow conditions.

The headlosses through the orifice meters are mostly due to flow separation caused by the sudden expansion of the pipe.

The headloss through the rotameter is larger for your high flow case compared to the low flow case, which indicates that the headloss increases with increasing flow rate.