If you come up I5, you have only two logical options for getting from south to north. You can just say on 99 and go through the tunnel, then up Oak street. You could go through downtown to Stanley Park and over the Lions Gate bridge and on to Highway 1 to Horseshoe Bay and beyond.
Alternatively, you do the tunnel & Oak street and head east to get onto Hwy 1 over the second narrows/ Ironworkers memorial bridge. I don't see any benefit to that route; not time or scenery.
One other deviation is to get on to the 91A road and go over the Alex Fraser Bridge, then the Queensborough Bridge and then head west on Marine Way. Semi- scenic at best.
Personally, I'd just do 99 through the tunnel and make that part of the trip direct and tiresome. If you do, be sure to take the HOV lane exit; it will get you around the long traffic line up for northbound traffic into the tunnel. It is 4 lanes, but they do a 3 & 1 config. in the direction of rush hour, so northbound traffic in the aft will be backed up for quite a way.
Once over the Lions Gate, you could opt for the Marine Drive seaside route. Slow but pretty and it will get you to Horseshoe Bay, with a bit of back tracking to get into the ferry line. May or may not be worth it. Once into Langdale/ Gibsons, it is a nice ride.
I can try to offer more specific guidance through our crowded streets if you want, but I may pick the wrong road just as easily.
Happy to send contact info if you feel it would be of any benefit at all.
BTW, if you have time, the ride north from Powell River is really nice. Depending on your ferry preference from Powell River to Comox, you could do the ride to Lund and back.... About 1.5 hours each way? Or, stay overnight in Lund. Pub at the hotel does great mussels in a coconut cream curry. That and the kale & beet salad do the job. With beer, of course. (Beer & Food; its why we ride. Full Patch members of the club get a Hi Viz lobster bib).
Hope you have a great trip!