Yes to above.
As a Washington resident it over rides whatever else you may own or have for conceal carry. So as a resident of WA go get your WA CPL (concealed pistol license).
As a non resident visiting Washington State - Washington State recognizes other states (See current list with WA Attorney General Reciprocity list)
https://www.atg.wa.gov/concealed-pistol ... eciprocityThe Idaho Enhanced License is recognized by WA State. But only as a non resident. As mentioned above as a resident of WA you need a WA CPL.
Most states require you to have your home state permit/license before applying for any non resident conceal. WA hasn’t gone that far yet for non residents but has made it required to have WA CPL if a WA resident.
As for notification or letting King County or any county/local LEO know in WA. No