I think for secondaries you could have done more, the flaregun and the shotgun are definitetly sidegrades but it's important to choose them well as they have a big effect on the pyros role. Flares are good for having a ranged presence, when you can't afford to extend at all you can still put the pressure on with flares. It reloads itself so you can put as many out as you like without needing to reload avoiding 'airblast downtime' I guess I'll call it. The flaregun does this fairly ok, and comes with full crit burn damage on burning players which is pretty nasty with afterburn. The manmelter.. I mean I wouldn't use it, but there's a perk you missed, and that is the projectile twice as quick as flares, and thats nasty when you have crits saved up. The detonator is probably also a sidegrade to the flaregun and shotty and doesn't get enough love at all. 1. it allows the pyro to selfdamage himself to build uber and even do rollouts 2. it allows him to reach good spots for ambushes and use routes he usually can't and 3. is it has huge ranged presence, the problem with the flaregun is at long range in open field, it is incredibly easy to dodge, and you can forget hitting scouts, you're dead. Not with the detonator, with a good sense of timing you will hit anything. You will light up scouts hoping around your teammates, and snipers out of view behind cover. I wont go over the shotguns advanategs because they're fairly obvious, hitscan, consistant dps etc.

Another thing I would add is relevance of afterburn, now the drawback is that it does build enemy uber, but lets face it the medic is always busy, and to have mutiple teammates running back because a flare got them or they got too close to the enemy pyro is disruptive. Paticularly if the medic is on fire too having his regen hindered. Pyro isn't a killer you're right, but he should be the guy punishing enemies who over extend, if a teammate is fighting an enemy you should be there to neutralise them with airblast, or light them up. The pyro can cause disruption and kill weak enemies better than any other class in my opnion. If they're hurt or alone the pyro can make an easy meal of them, or even a battered crowd. If you debuff a few members of the enemy team with afterburn they're gonna very predictable and wanting to heal and that makes them easy picks for your team.

Lastly, I mean I wouldn't argue this too far, but I do think some nasty flanks and ambushes can be made in highlander when appropriate, very easy to make an uber pop, or with some luck actually kill or assist a kill on the medic. Worse case scenario is you leave their team on fire and a bit wtf, teams don't push or hold their ground when they're on fire. But yeah pretty sound guide all the same, big cheers for putting some time into and making sure everyone knows what they're doing

i'll add in those little bits of info about the secondary weapons + advantages of the higher afterburn into the video annotations - going on what you've said, the utility of the detonator might make it the most useful flaregun-type option, as does the possibility of lighting up people that you'd otherwise miss (and i can see the pyro, between pushes and once the spy is taken care of, doing a bit of flaregun spam in between reflecting stuff). also, i think that the right approach to take to the flank/ambush thing is that it's most viable when you know that they have kritzkreig, if it's normal uber then you're always best waiting to reflect the uber away. but like you say, it's only advisable to a certain extent in the first place