How do legendary weapon effects work with shotguns?

In doing some weapon research, I've read that others prefer the "Explosive" legendary effect on shotguns and laser weapons with the beam-splitter, since they've reported (such as here) that each separate pellet/beam of the shot will gain that effect. There are a few other weapon effects that seem to affect on a "per shot" basis which leads to a few questions. Namely:

1. Freezing/Incendiary/Irradiated/Plasma-infused/Poisoner's/Two-shot/Wounding: Are all of these effects also on a per-pellet basis?
2. Staggering: Does each pellet have a chance to stagger?
3. Instigating: If an enemy with full health is hit with, say, 4 pellets, will all 4 of them get the 2x damage bonus for Instigating? I suppose the answer to this could be dependent on whether or not all pellets of a shot "hit" at the same time.

Solution 1:

Per Shot: Irradiated, Freezing, Plasma Infused, Incendiary, Poisoner's, Furious.
Per Projectile: Wounding, Explosive.
Untested: Status effect only legendaries (Kneecapper, Stagger, etc.) and damage multipliers (Powerful, Exterminator, Two Shot, etc.)

Damage-Over-Time doesn't stack. (Except for Wounding.) So even if they are per projectile, they are effectively per shot.

I just tested this myself with a couple sets of console duplicated semi-automatic laser rifles (maxed Rifleman perk, game version 1.7). Focused vs Splitter for each legendary tested. Used a brahmin as target practice (no VATS), and measured damage. There was no difference in damage with the per-shot legendary effects. By comparison, the split per-projectile legendary effects did vastly more damage than their focused counterparts.

Solution 2:

1)Freezing/Incendiary/Irradiated/Plasma-infused/Poisoner's/Wounding: I know for sure all these get the effect for every pellet. All you have to do is look at the damage they do when all the pellets hit a single enemy or the fact you can deliver the effect on 2 enemies close together with a single shot if the pellets hit both. I'm not sure about the two-shot effect though don't see a reason why it wouldn't but haven't seen a shotgun with that effect yet.

2)Staggering: I'm not 100% sure about the staggering effect but I would say yes just based on the fact you can perm stagger enemies with a combat shotgun with this effect even legendary enemies.

3)Bloodied/Instigating: Bloodied is based on the players health the bonus is better the lower your health is and each pellet gets the bonus fine. I haven't seen an Instigating shotgun yet so I can't comment on how the effect would act it would be 100% speculation.