In modern aircraft, TOGA is usually a combination of thrust and pitch control, but some installations allow independent operation.
After mode selection, a representative thrust level should be indicated on the primary power instruments or thrust management system, and with autothrottle engaged, this thrust level is achieved automatically. This is often referred to as ‘takeoff thrust’, but the mode of operation can be used for either takeoff or go around, not necessarily at the same thrust level.
The pitch mode is primarily speed referenced commanding attitude, but may involve some acceleration; the speed value is normally the climb (safety) or approach reference speed plus a bit, but the addition might be reduced with engine failure (alternative systems may use or mix angle of attack, and have stall protection).
The pitch reference attitude can be shown on the flight director for manual flight, and used by the autopilot if engaged.
For takeoff (TO), there is normally a requirement to be in the air and/or at a safe speed.
For go around (GA) selection, there may be an upper altitude limit and the need for an approach mode to be active (not necessarily autoland), but otherwise, depending on type/design, GA can be selected at any time until touchdown irrespective of flap setting.
Disengagement is usually by pilot selection to another mode or at some preselected altitude, to ALT mode.