We live in the Puget Sound area. Is the ferry/Stromma through the archipelago a similar experience to ferrying/boating in the San Juans and other islands?
I've never been to the San Juans so I can't answer that question. But if you have some more specific questions I can try to answer them.
Is the ferry/Stromma worth the time/money?
I’ve also never been to the San Juans. I think the Stockholm archipelago is very scenic. The Stockholm archipelago has some 30k islands and skerries. https://www.stockholmarchipelago.se/en/
There are various ways to see or visit the archipelago. If you take the ferry to Helsinki or Tallinn, you will sail through the archipelago. You can take a sightseeing tour. You can take one of the regular ferries to an island in the archipelago such as Grinda or Sandhamn or Utö. The companies Stromma and Waxholmsbolaget offer ferries and/or sightseeing tours.
Is it worth it? I think it is worthwhile when the weather is nice and you have sufficient time for this type of excursion.
I live in the Puget Sound area as well and have wondered the same! We are headed to Stockholm in a few months, and I am just now diving into the "to do" details. Enjoy your trip!