If you decide to transit Gillard Rapids, we have found the best time is a slack before the ebb. Maximum flow through the Rapids can reach 10 to 12 knots with strong eddies. Once through the Rapids you follow the ebb current north through Yucultas (pronounced youclatus) and Dent.
If you happen to make Gillard Rapids slack before the flood we layover in Big Bay until the next ebb. Much of the Bay is now private, but they have a public marina, general store and the hike to Eagle lake is quite nice.
A nice layover anchorage, or dock if you prefer, is Shoal Bay. Not much there, but worth a stop at the small pub to visit with the locals and peruse the history of the Bay. There is also an old logging road that will take you up to a scenic overlook of the Bay and further up to an open abandoned gold mine tunnel. Bring a good flashlight and watch for vertical shafts when you go in.
Regarding Johnson Strait, it seems that every day is gale day in the strait, especially in the afternoon when the onshore NW breezes pickup. The mountains on either side of the Strait also has a Venturi affect on channeling the wind velocity.