Tech Tree / Direction / Sale Help

My main things I’m planning to get in the sales are for Britain (Khalid, Sea Vixen, Sea Harrier Talisman(?)), Sweden (J29A Talisman, Leopard 1A5NO), and France (AD-4NA, VBCI-2), and I want to know whether I’m making a mistake here. While I’m spending most of it on premiums, I have quite a decent reserve of GE that I’m putting into Premium, and some spare change of crew slots + points.

I’m mainly interested in the British air tree because I love the Harriers and (in the future) Eurofighters, and I’m pretty much set on them. The ground on the other hand is an interest because of the Challies and Cheiftains (favourite MBTs), so I’m pretty deadset on that too. On the other hand, the French and Swedish I’m unsure of. I want to get the Viggens and Gripens for Sweden, but I don’t really know whether I should ditch France and spend the money elsewhere.

Largely I’m asking:

a) What do they do well at?

b) Which would be more worth it?

c.1) If not, should I aim to grind America (Already have the BTD, A-4E and T14 Heavy, with the potential to aim for the YAH-64 or M1A1 AIM), the Soviets (already have the MiG-21S-R13-300), or something else?

c.2) In terms of playstyle, for Air I like jack of all trades with a focus on agility and dogfighting capability (like the Spitfires), and in ground I’m looking for something that’s either punchy and well-armoured, or fast and responsive.

If you read all the way through this, much appreciated, and I’d like as much help as I can get. Cheers :)

Just to note, I’m also 160k RP away from getting the F-4EJ Phantom II, but I’ve lost some interest in the Japanese Air Tree, largely because of burnout from constantly playing the T-2.