Are there any helicopters where the main rotor head is at the same level as the tail rotor?
The answer is yes, they all do in a certain part of the flight envelope - probably the cruise.
Certainly Brit military Principles of Flight teaching is thus: put simply, tail rotor roll (ie hovering left or right skid/wheel low, depending on main rotor direction of rotation) IS a consequence of the different height of main and tail rotors and is designed in to avoid being left (or right) side low in the cruise. As the fuselage pitches further down with increasing speed, at normal cruise, you have a (laterally) level floor. Much more comfortable, and less disorientating in IMC. However, inevitable design compromise means that laterally level fuselage in cruise (tail rotor and main rotor level) inevitably means in the hover when more nose up (tail rotor and main rotor NOT level), there is a lean to one side (towards the advancing main rotor blade).
Check out side on pictures of most conventional helos in the cruise to see that tail rotor is usually level with (or closer to) the main.
And I did say "put simply"!! With due consideration for Danny's bandwidth.