It's surprising to agree on something with one of Dredgens and at the same time with TMJ99. You should not infuse ever until you hit the soft cap of 900. Unless, you got a sword as heavy weapon and you need distance. Even blues will drop 10 above your current level. I hit 903 yesterday with my hunter and it was just boring to do so because I got my light levelled up 40-50 levels only opening the region chests (admittedly, you don't pay attention to those in general). I fully opened Moon, tangled shores, IO, some left in cosmodrome and so on. If you use your legendary rewards before 900 to level up, you won't get those campaign quests again but will have to do weekly routines to level up your gear. I have not tried using ormanents as I'm still just collecting higher tier armor (highest I got totals up to 56 point on the armor) can't comment on if it provides any tangible benefits to not looking lika clown for another year. However, if you look at the cost of infusion with considering they have added more materials to grind for its gonna be more grindy game. You'd be playing to get better armor and mods for it than play for fun and do as you like. Not sure if it's gonna be super bad or 0.4 kinda change at the end. If I were you I'd refrain doing anything you need to spend so many materials. Destiny 2 was never a game that you know every details because games informs you how things work. Wait and research not to waste materials.

Given how it really hasn't changed, yes

It's not. It's too early to tell though because you really shouldn't be infusing anything yet except a couple weapons.