I paddled part of that. Lesson learned: Get seamanship
Athletic ability is only one part of the equation. Learn as much as you can about the ocean before you go.
Three others and I sea-kayaked the IP from Ketchikan to Skagway in June 2004. We had paddling experience but were not true ocean paddlers. Meaning, we had tide tables and understood what happened with those, but we went without any charts or tidal STREAMS info (a.k.a., the tidal currents). Also did all our "navigation" by visual piloting. We only had topo maps, which are useful for figuring which parts of shoreline would make decent campsites (and where fresh water from streams is available), but we really should've had nautical charts as well. Charts indicate all kinds of marine info that could be important, such as beacons, buoys, water depths and obstructions underneath, various kind of hazards, and lots more that is NOT shown on topos.
While we did not incur any disasters, there were some dangerous conditions that we were simply lucky to push through, and a bunch of others that would have gone much more efficiently if we'd known more about ocean paddling. (You wanna get stuck on tidal mudflats for 4.5 hrs like we did one time?)
You might be able to bull your way through without learning "all that boring stuff" but you put yourself at much higher risk. I can't possibly overstate this.
Timing-wise, IF you plan to do it in summer, the prevailing winds come from the south. So you'd probably do better if you went south to north. The normal weather is gray and spitty/drizzly with very light wind. The clear days are the ones that get wind coming from the north, and it's likely to be stronger wind then.
Take bear precautions when camping. AK coast has both black bears and grizzlies. Keep a totally clean camp, pack out your trash that can't be burned to ash, etc. Yes, this means you will be hauling trash in your boat. There are a few towns where you can dispose of it (and eat in a restaurant! Burger and fries will never taste so luxurious!).
I don't know about the southerly part of the IP, but the section we did consisted almost totally of barnacle- and seaweed-covered large rocks for "beaches." There were a few cobble or coarse gravel beaches, but they were rare treats. Secure (tie) your boat if you can't bring it all the way above the expected high tide line PLUS extra margin for big ship wakes or storm surge. Sometimes that meant we had to carry the boats into the forest.
What else...if you can't pack all your food from the start, you can send care boxes to General Delivery at towns along the way. We mailed boxes to Petersburg and Juneau.
Study the Alaska ferry schedule and their requirements, assuming you are not rowing the IP as a round-trip. They allow bikes and kayaks on board but I don't know about rowboats or other vessels. If you want to take a car on the ferry, you need to reserve waaaaaaaay ahead of time, and it's expensive.
Robert Miller's book is a good guide to the IP, all 1200 miles of it. Other books are mainly anecdotal, though still interesting. I'd add the one written by a former park ranger (Tim Lydon?) to that bunch; think its title is "Inner Passages" or something like that. He and a friend paddled from Port Hardy to Juneau.
Just as important, look up the Coastal Pilot for that part of the PacNW. It's free to download from NOAA's website. You can also download the relevant nautical charts from NOAA. And learn how to read them, as well as use a compass on the water. Fog happens.
Understand how the phases of the moon affect both the tide highs and lows AND the maximum tidal stream speed.
And if you carry a GPS in addition to a compass, make sure you bring lots of extra batteries. Our group had 2 GPS units, and on many days one of them had dead batts. Some days, BOTH had dead batts.
Besides, you'll want to carry a VHF radio that you know how to use properly (i.e., don't scream Mayday when Securite or Pan-Pan is appropriate).
There's so much more to planning such a trip but you get the idea: don't treat it as only an athletic endeavor. It's a beautiful, beautiful place that deserves your respect.