Lazy:

Before I can tell you if the open shove is correct, we'd need to also establish what would happen if we tried OTHER plays.

That's what you are ignoring. It's not enough to be +EV. I suspect any play other than folding a big PP is +EV. It's whether it is MAXIMIZING EV.

As for never varying your betsize postflop, there are actually interesting issues about balance and exploitation there, as well as problems with lack of information. But one big difference is that when we are playing postflop, we have a lot more information about what our opponents have. When we don't have that inforkmation, it seems to me there's a stronger argument for balanced play.

But we do have information. We have a good idea of what types of hands villains will fold/call/raise with preflop. In fact, we have more information since preflop stats converge much much quicker than post flop stats. There isn't a need to balance when you're playing against horrible players, not sure why you just won't admit to that.

In the shoving example I gave, I said you will always be called by 2 players both 100bb deep. That means you will always be playing a 300bb pot with the nuts. Now clearly, in order for 2 players to always have a hand to call you, they must be playing fairly wide ranges, so fair to say that Hero wins at showdown at least 50% of the time, so he's profiting at the very least 100bb per hand.

You're never going to get a better informational edge than that by raising to only 3bb preflop. You do realize that you're basically advocating playing small ball against droolers right?

No offence, but what this sounds like is you have had some conversations with some online pros and have taken something they've said out of context. Some $5/$10 SNE grinder might have said something along the lines of don't vary your bet sizing preflop, but I guarantee you that the reason for it is because somebody like Nanonoko is going to figure out how to exploit them for it, and nowadays, there's pretty well always at least a few sickos like Nano at every $5/$10 table.

Now if you go back and ask those same guys how they would play if they were looking to maximize their winrate at .01/.02 I can almost guarantee any good mid-high stakes player is going to tell you to vary your bet sizing pre and post flop because there is no reason not too. You dont need to balance, everybody is just playing their own cards, and even the winning players at 2nl are basically just playing their own cards but they just do it a lot better than the typical drooler.

I realize my example is a tad extreme but I only used it to illustrate how shoveling as much money into the pot as you can get away with for value is going to be superior than small ball.

Big hands benefit a lot from smaller SPRs against drawing hands because it is easier to get the money in on the turn. With larger SPRs you need 3 streets to get all the money in. Fish fold the river with their busted flush draws but will often still stack off for a pot sized bet on the turn. When they call the turn with more money behind they make some of the money back from their bad call since you can't always just c/f the river everytime a 3rd flush card comes in.

But we do reduce our edge the smaller the SPR is. Big SPR = bigger edge against bad players. I think i learned that from a AEjones video not sure dont remember it exactly at the moment

This is true. We should always want to play with deeper stacks against fishier players. That does not mean that we should always try to keep the SPR's large against players that will happily call large bets and raises with mediocre or plain junk hands.

If all we care about is having a large SPR so that we can have a huge edge then why don't we just limp our entire range preflop?

The answer is simple, we want value from our big hands and we want fold equity with our bluffs.

How should the raise be 30% "By definition?".

The point of the example was to establish a situation where our opponent is making some very major deviations from what is considered "good" play preflop, and is vastly better than us postflop. Assume, if you'd like, that they are a very good player postflop, and we are very bad postflop. You could fiddle with the numbers a little, I just wanted to set up something that made it clear that we were vastly outmatched, but that our opponent was making some serious "errors" preflop.

You can't? Even if your raise size has no effect on what hands they call or reraise with? Or, to be more realistic, they do not adapt sufficiently to a given change in raise size?

Therein lies the continuum, though.

Larger raise sizes may = more value, but they also = costlier bluffs. And since we assume that even the worst players will eventually pick up on raise sizes that are strictly tied to the value of the hand, there's a strong argument to picking a raise size that makes our bluffs look a little value-y and our value hands a little bluff-y.