Immediatelyl. Generally, if everything went well with the root canal therapy it would be a good idea to start immediately with the fabrication of a crown. Only when the prognosis might be guarded due to a number of reasons, would it be wise to make sure the rct is successful prior to making a crown for the tooth (just in case the rct fails). Discuss this with your own dentist.
Depends. My collegue gave you excellent advice. There are many myths about when to crown.I have heard everything from immediately , 1 wk, 2wks, 1 mo, and so on! whenever I do a root canal, part of my records states when to crown. Most cases can be crowned immediately. The importance can't be overstated. Posterior teeth are protected by crowing. In certain anterior cases, no crown may be needed ask your dr.
Be patient 2 weeks. It doesn't have to be done ASAP, unless you have a massive filling or tooth distraction. Two weeks is a reasonable waiting period. .
Your Choice. A correctly placed post and core needs to be placed first to make the tooth strong (like why rebar is placed in concrete). Then a crown can be placed at any time.