Good generalized summation, tough subject to discuss outside of a specific state forum though.
I don't normally make the comment but IANAL, since this is a general forum, that said...
Easiest thing to do is determine your status before you walk away, ask "Am I being detained?" If the answer is "No", then leave, no comments or parting quips, just move away,preferably to private property to end the encounter.
If the answer is "Yes", then "I decline to answer any further questions", this is where you may get a "terry search", depending on your state you may want to make a further utterance to clearly retain your rights (depending on state)
If arrest follows "I wish to speak to an attorney" and remain silent thereafter (depending on your state you may be required to provide identity and/or ID at this point your laws may/will vary.
There are multiple threads on "Don't talk to the police".
Now back to RAS, the part I have found and it may be specific to WA, is that the LEO has to have facts, not hunches, guesses or reasonable assumptions that add up to a suspicion, if he doesn't have enough and each state varies on this, he may be constrained by the state's laws in how much investigation he may do.