To tie in or leash or nothing. 

Most opinions I've heard are that leashing on WW is a bad idea.  Too many ropes to get hung up & tangle the canoe in a situation where it would otherwise have floated clear.  People are pretty split on tieing in or allowing your packs to float free of the canoe.  Even tied in they provide opportunity for the canoe to get hung-up on something it might have bounced/floated over.  Bill Mason said let them float free.

There's a salient difference between float bags & packs.  Float bags add flotation as well as displacing water when the canoe is swamped.  Packs don't offer the same flotation in a swamped canoe.  Neither provide any floatation until the canoe is swamped.

I'd say don't be afraid to drill.    (You need to Login or Register

For overall versatility I think a spray skirt would get more use.  Keeps the rain out.  Makes big water more navigable, less worry of getting caught when the waves whip up.  Bags being more like a parachute, uselss until you actually need it - then you really want to have it.  Preventative vs. curative.