Selecting another pitch mode (VNAV or LVL CHG) or engaging an autopilot terminates the TO/GA pitch mode, so your discussion is only valid for manual take-offs.
AFAIK, the TO/GA pitch mode commands:
- 10 degrees down to 60 knots, then
- 15 degrees up, until "sufficient climb rate", then
- V2 + 20 knots, in MCP speed mode, although TO/GA is still displayed, because
- If an engine failure occurs, the engine failure speeds of V2, existing speed, or V2 +20 will be commanded.
I would say that for all normal (i.e. non-engine failure cases) the TO/GA and LVL CHG pitch modes are identical MCP speed modes.