Most effective way to improve cantilever brakes I have a Dawes Super Galaxy touring bike with cantilever brakes, and I'm a bit worried about the stopping power of the brakes when I start loading the bike up with kit to go touring. But I don't know what the most effective method to improve the braking power would be.  I've listed below some options I would consider, but I've also included what I don't know which could affect each measure.

Change the brake blocks. Perhaps more expensive brake blocks are much more effective.
Check your brake adjustment. Perhaps there are common and simple mistakes people make when setting up cantilever brakes.
Change to newer cantilever brakes. Perhaps the old style cannot be fixed and it's best to go for more modern cantilvers.
Change to a different type of brake. Perhaps cantilevers as a whole just aren't very good and my forks are compatible with a different brake style.
Buy new rims. Perhaps my rims are made of a notoriously slippery material and changing anything about the brakes will never have that large an effect.

I'd be grateful if people could point me in the direction of finding out which is the single biggest change I can make for better braking performance.
A few notes:

I tried to follow this park tool video when setting up the brakes: Brake Caliper Mounting &amp; Adjustment - Cantilever Smooth Post

I have these brake pads as spares but I haven't fitted them yet: https://www.sjscycles.co.uk/brake-blocks/aztec-control-block-cantilever-brake-blocks/
My current brakes look more like this than this - i.e., long arms which stick out horizontally rather than starting vertically from the bosses before curving out.
I have these brake levers, which have a setting compatible with cantilevers: https://www.sjscycles.co.uk/brake-levers/shimano-sora-blr3000-flat-bar-caliper-brake-levers-222mm-clamp-black/
Pad quality makes a huge difference on rim brakes. While the spares you have may be better than the old pads, they're still going to be far worse than a good pad, especially in the wet.
I have a BSO with early V-brakes that take canti pads, and have been pleased with these Kool Stop Eagle 2 dual compound.  The dual compund (soft and hard) is key to all-weather performance. I use similar pads on my hybrid with proper V-brakes; both the stopping power and the wear are far better than with cheaper pads.   XLC make some dual compound pads that stop well but wear faster than those Kool-stop pads.
When setting up cantilever brakes,  pay particular attention to:

The pad clearances. Set them almost as close as possible to the rims at rest; true the wheels if you find you've got to back off the pads to avoid touching the rims at certain points in the rotation.
Setting up the straddle cable for maximum mechanical advantage (from about 3:50 in your Park Tools video).  This is about how hard the pads press the rims for a given hand pressure, but good mechanical advantage shortens the travel of the brakes, hence needing the pads to rest close to the rim.
Do make sure that the straddle cable can't drop onto the front tyre if the main cable snaps, especially if your tyres have plenty of tread - a mudguard or reflector bracket can prevent the wheel suddenly locking up from a dropped cable and causing an unlikely but serous accident.

With good pads, well adjusted, cantilever brakes are almost equal to V-brakes in stopping power; the main advantage of V brakes is their simplicity.
The Galaxy series has been around for a long time, so your bike could be quite old (on the other hand it could be from last year).  If it's an old model, not only could the pads have hardened with age, there's a slim chance the rims are steel which is rubbish for braking. I'm not sure it was ever sold with steel rims (and almost certainly not with steel rims and canti brakes), but on an old bike I'd check anyway.