[Speedlimits]

Nice post.

I think when deep stacked (I define deep stack as 200BB+) the preflop game becomes negated to a degree. For instance my 3betting range with 100BB's is ridiculously wide from a Btn open because #1 Most people play more hands from the Button which means on average their hands will be weaker.
#2 The raise is a larger % of their stack which means postflop skill is less relevant.

Now with 200BB's I think 3betting ranges should become more polarized. 3betting suited connectors/small pairs/KK-AA and flatting AK/10's-QQ's preflop seems like a good adjustment.

You want to maintain the value of mediocre-good hands by flat calling because 3betting deep leaves you exploitable by
A. The light 4bet as A5 mentions.
B. The legit 4bet where you completely lose value with good but not great hands.

The whole allure of 3betting pf when 100BB is the defining of hands. When someone raises you 10% more of your stack you are forced to make a decision. Even more threatening than that is the potential future bets opponents will have to call, this is why 3betting with 100BB works so well.

When 200BB+ deep that threat isn't there or it is but to a lessr degree. Since now it is ONLY 5% of your stack you are being asked to put out before you know the flop. From a pure game theory perspective we know that no reasonable hand you would call a 3 bet can be more than a 4:1 dog. So even IF you are a 20% favorite it still benefits you to make that call given the implied odds.

In conclusion, polarize your 3betting range when deep to premiums and junk and flat call pf with your medium strength-good hands.