In the Oz AIP (quotes below may be a little old) if a pilot reports visual then it's an indication to the ATC that they can make a visual approach, however for "International Heavy"'s they must specifically "Request Visual Approach" to be cleared for one. (Excluding Sydney parallel ops)
As for tracking (day time ops):
Tracking Requirements. Tracking requirements for a visual approach include the following:
a. A pilot in command must maintain track/heading on the route progressively authorised by ATC until:
(1) within 5NM of the aerodrome;
This means continue to follow the heading to final if outside 5NM or the STAR you were flying etc until 5NM. Once inside 5NM you can do what you want unless you were told to do something specifically by the ATC (ie track to a 3 mile final Cleared Visual Approach runway 23)
As for altitude:
11.5.5 Minimum Altitude Requirements. During the conduct of a visual approach, a pilot must descend as necessary to:
a. by day:
(1) for an IFR flight, remain not less than 500FT above the lower limit of the CTA; and
(2) for IFR and VFR flights, operate not below the lowest altitude permissible for VFR flight (CAR 157).
So unless specifically instructed you are able to descend as you wish as long as you stay in CTA (plus buffer) and also avoid 'buzzing' houses etc.
There is no such thing as an "unrestricted" visual approach; it's either a visual approach (which is unrestricted unless otherwise specified) or it's a visual approach with (altitude or tracking) restrictions.