Pre-LHTR Lend Lease is insane. Non-LHTR Super-fortresses is also pretty crazy.
Colonial Garrison makes KJF much stronger. Radar messes with things a lot. Mobile Industry makes the Caucasus no longer a vital country, and increases the strength of a KJF. Mechanized infantry lets you do a lot of stuff, as does fast carriers, as does island bases . . . really, MOST of the Allied NAs are quite good.
Germany’s Blitzkrieg is decent because it frees up fighters. Japan’s Banzai is okay. (Banzai’s not great against a KJF, and even for a KGF, you need tanks and fighters for that last push into Moscow). Most of the Axis NAs suck. It is usually a matter of HOW MUCH they suck.
How to abuse pre-LHTR Lend Lease - UK fighters, US fighters. You haven’t seen “stupid” until you see Russia producing 8-9 infantry a turn with 14 fighters for backup. No, seriously. Russia just beats the hell out of everything. LHTR changed this, thank goodness.
How to abuse Superfortresses - build bombers to strat bomb, go for tech dice on US3 or US4. With heavy bombers, you shut down Germany. LHTR limits total damage per turn, I believe, instead of total damage per bomber, so stops this from doing more than 16 IPC damage.
How to abuse Blitzkrieg - well, you take this fat load of tanks, and use 1-2 infantry to trade territories with Russia early. Since you can use your tanks to trade territories without committing, now you can use your fighters for other things. Like . . . getting EVEN MORE territory, or fighting off that Allied Atlantic fleet.
How to abuse Banzai - use a lotta infantry, surprise.