I just came back from the Broughton’s.
Challenging part there is to get across the Johnstone strait ( 4-5 km crossing) as it is often windy with waves. The next challenge is to get through either Blackney passage or Weynton passage which have dangerous rips and whirpools.
We did the Wheynton passage going back to Telegraph cove at the low tide slack (Alert bay), it was not too bad but hard work to go against a strong current and somewhat disconcerting as whirlpools suddenly emerge in front of your kayak. On the way north we started from Kaikash creek at the lowest tide, so got to Blackney passage about an hour after low tide slack. There was a current there and eddies but managable.
Add to that a possibility of a cruise ship going through these passages (mostly Blackney, moving slowly, smaller wake) but also straight down Johnstone strait at high speed creating a very large breaking wave. You can listen to the shipping traffic on Channel 71 to know if a big ship is coming.
To avoid all this you can take a water taxi at Telegraph cove to get over the Johnston strait and the passages.
There are lots of commercial groups paddling there so be prepared to share a campsite. Kaikash creek is a large campsite with orcas parading there every evening. There was a humpback there as well plus lots of humpbacks in Queen CHarlotte strait.
Hope this helps,