It seems logical that you can use the Ready action to prepare to grapple or shove an opponent if triggered. But can you just Ready an attack, and then decide when it’s triggered whether to attack as normal or try to grapple or shove?
Similarly, you could certainly Ready a specific weapon attack like “if a creature moves within 5′ of me, I swing my mace” or “if any of them draw a weapon, I shoot an arrow at them”. But could you just say “I Ready an attack, if any of the creatures move close to us?” and then, when it is triggered, decide which weapon to attack with, whether to attack with melee or range, or (as above) whether to use a weapon or grapple/shove? Or disarm?
A similar situation is Help – you could be planning to help one character do something, but by the time of the trigger, prefer help someone else do something else. Could you just say that you are Ready to Help whoever might need it when (trigger)?
Essentially, how specific do you have to be about the Action you are Readying? Can you be as general as saying you will Ready a move, an Attack, a Help, etc.? Or do you have to say who you will Attack, how (melee/range) and with what weapon, or who you will Help and with which of their Actions, etc.?