Deadball foul by B after try is marked ready.
 

I don't have my book with me to look this up.

Fed Rules:

Foul by B after marked ready for play on try but before ball snapped ( i.e. encroachment or personal foul)...is A given option of enforcement on try or kickoff or is it enforced on try?

There is no option because the foul did not take place after a scoring play or during a scoring play. When the ready is blown in, that brings in a different set of circumstances. If accepted it is enforced on the succeeding spot.

Peace

Deadball foul by B after try is marked ready
 

that is the case in which there is no option. if A/K accepts the penalty, it gets enforced on the try. no carryover.

But if they are kicking the try, and already set up for the snap from the 3, A often does not want to move the tee.