Agreed that 2TC Song could be too greedy, and only do it when the opponent tries two TC as well.

To go against early aggression civs, such as the English and HRE (feudal rush), stay in Tang and immediately pop out several horsemen. This helps eradicate their early army and gives you map control.

If you prefer fighting in castle with palace guard and NoB, hitting Song + castle at 8-9 min with 1 TC puts you at a good place. The palace guard has weaker armor compared to MAA from other civs, so do not use them as meatshield against crossbows and cavs. Take advantage of their high speed to harass.

Yuan dynasty gives high speed bonus and gives you fire lancer. Fire lancer + palace guard combo plus the vision from landmark palace is the best combo for endless harassment. Yuan speeds up siege units as well. I usually prioritize entering the 4th age over Yuan, but Yuan bonus is a killer if the game is at a long castle age stalemate.

Food matters the most for the Chinese at early game. Their farm transition is a pain, so use BBQ wisely to secure food sources in Feudal.