Not quite sure how we got onto VFR departures, but back to topic!
You can arrive in a circuit pattern at an airfield at any height you choose (subject to company and local regs and safety) and from any direction as long as:-
a) It is safe
b) Everyone, inside and outside the cockpit who needs to know what you are doing does.
The g/a from a visual approach would 'normally' be into a further visual circuit.
The height for a visual circuit is likewise yours to choose subject to the above. I once watched RAM at GMMN flying round the pattern at 500' and quite enjoying it!