On topic, I’ve always been against the G1 AC buy (or any naval buy for that matter), but I think there are times and situations where it can work, but I generally prefer to focus on land buys (perhaps air) with Germany. Although, I’ve been kicking around the idea of all land buy on G1, then maybe an AC on G2, if UK didn’t hit the Baltic fleet. It worked in one game and the idea is, UK sees no reinforcements but buys a plane or two to sink on UK 2, then Ger drops the AC forcing the UK to re-evaluate things now on UK 2 and hopefully catching them and the US a bit off guard since they spent their rd 1 purchases and NCM expecting one scenerio and then they have to deal with another. You also have the opportunity to judge Rd 1 and Rus 2, is a dash for Moscow an option or did Russia roll down twice (no AC on G2) or did Russia roll up meaning you just want to buy time for Japan (maybe AC buy).
I’ve never regretted buying Inf/Rt/Arm, but I have bought navy before and sometimes I wish I just had the Inf.
As for the KJF questions, IMO it is definitely viable regardless of ruleset or victory conditions.
While it gets hard to define I’d probably define a “true” KJF/KGF as something that is 3 on 1. You use limited resources to “contain” the other side while the main focus is on taking out the other Capital or severlly crippling it.
You can choose to ignore one of the Axis powers b/c in theory you can cripple the other long before the one that is left alone can take Moscow.
In KGF, the three Allies kill the German ships and box German into WE, SE, Ger, and EE while you stack Kar and Wrus. Now Russia turns to defend against Japan and the UK/US can lend support to Mos if needed or just continue to squeeze Berlin.
In KJF, the UK keeps Germany honest in the Atlantic with a little US help, but the main thrust is an early all out assualt on Japan (maybe UK and US ICs) in Asia with a massive US presence in the Pac such that by mid game it is clear Japan will never be able to match the US buying power and they can then keep Japan in check as UK switches more and more to aid Russia or go after Germany.
It is easier said then done but those are the theories.
If I go after Japan I prefer a somewhat delayed KJF approach, which is more like a US only Pac strat, it may not be optimal in terms of really getting after Japan, but it allows me to see all the way up thru J1 before I commit to going after Japan or Germany.
Although I may start trying a more “convential” KJF approach in the future just to change things up a bit.