Your understanding of the incentives seems sound. But there’s a lot of nuance here, and tbh it’s impossible to answer all of your questions honestly without writing a massive wall of text. Try narrowing your questions down a bit. I'll focus on the SB aspect of your question.
Some food for thought:
- How wide you can 3bet is mostly a function of the aggressor's range rather than their sizing.
- How wide you can call is mostly a function of pricing and equity realization. Facing a 2.5bb open, any SB hand that recoups at least 2bb can call (although a raise might be more profitable).
- The idea that SB never flats is just an oversimplification. SB almost always has a flatting range, although in high-rake cash games it's so slim that many simplify to a 3bet or fold strategy.
- You could change your range to flat more in SB, but that requires more protection, so you’d need to sacrifice the EV of a 3bet with some nutted hands that now call.
Analyzing GTO ranges:
You can view these for free on GTO Wizard if you make an account.
Here's a SB chart vs BTN open (2.5bb) from GTO Wizard with a NL500 rake structure. There's not much calling, so this can be simplified to a 3bet or fold strategy.
Here's how SB reacts to a UTG 2bb open (NL500). There are a lot more calls.
The difference here is that
1) UTG's tighter range prevents BB from squeezing too frequently, so your calling range sees a flop more often.
2) UTG opened to a smaller size (2bb instead of 2.5bb), so SB has better pricing on a call.
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Now here's a SB vs BTN 2.3bb open for 8max MTT (100bb). Way more calling, and wider in general.
The difference here is that:
1) BTN opened smaller, giving SB a better price on a call.
2) BTN opens 10% wider (due to ante), so SB can continue wider.
3) There's no rake.
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As you can see it's not that straightforward. Even the bullet points I gave at the top of the post are oversimplified and missing information. But that's the nature of trying to describe a game this complex in a forum post.
Last edited by tombos21; 07-05-2022 at 10:14 PM.