If your loop begins and ends in Vancouver I would not include Seattle in your ride. Vancouver is an easier city to ride in. You could easily follow the ACA Pacific Coast route from Vancouver south. Check the online version at this site.
http://tsteven4.qwestoffice.net
If you want to go to Seattle you can easily get to it from the ACA map.
If going to Victoria via the US you can either get there via the ferry at Anacortes or Port Angeles. I would do the latter. Once on the island there are several options for rides north of Victoria. If you have the time I would recommend going up to Comox and returning to Vancouver via the Sunshine Coast as per your option number 2.
Most of the riding can be done using reasonably quiet roads.