Tail rotor drift occurs because the TR has to produce an anti-torque force to oppose that produced by turning the main rotor - on an R22 rotation (anticlockwise viewed from above) the gearbox pushes the rotor round one way and tries to turn the fuselage around the other way (equal and opposite reaction).
The TR produces a force in an anti-clockwise direction to oppose the clockwise rotation of the fuselage but in doing so creates a drift to the right for the whole aircraft - this is opposed by left cyclic tilting the MR thrust and giving the left wheel/skid low hover attitude - there is now a couple about the C of G between the TR thrust and the horizontal component of MR thrust.
The mass of the aircraft acting about the C of G along with the vertical component of MR thrust act as an opposing couple and the resultant attitude is a balance of the two couples.
The canting of the tail boom to elevate the TR is a design issue depending on what the aircraft is designed for - aircraft designed to operate mainly in the hover will have a raised TR so that the MR hub (horizontal component of MR thrust) and the TR are reasonably aligned in the hover giving a more level cabin - aircraft designed for high speed cruising will tend to have a straight tail boom so the TR is aligned with the MR hub when the attitude is nose down for forward flight. This is a simplisitic and not definitive answer based on older helicopter designs since modern aerodynamic fixes (canted TRs, clever horizontal stabilisers etc) mean that it is not such a clear cut division.
Ray Prouty often states that with helicopter design 'what you gain in the hover you lose in forward flight and vice versa'.