The game is all about priorities--this isn't PG

. You have to prioritize your forces for the objectives. You can spare forces for other matters (such as taking more cities or destroying the rest of the AI ground and air forces) only once when you have achieved some level of force overmatch.
For air I protect my forces and use other to soften up the objectives or next area I am attacking towards. The close and deep fight. If the scenario has lots of water and the chance of ships then I bring good strategic bombers with anti ship capability, but I do not go hunt ships until they are a threat.
Fighters must protect bombers while enemy air is active. Only once you have superiority can you stop escorting the stukas. The 110/210/410 is another matter, they can take care of themselves until DLC 43 and later. I wish the air gave better recon as it flew across the map, but the recon is only a tertiary function.
Ground Recon cannot get too far ahead. They must recon and screen or guard your force and be preserved. They cannot go off and take objectives very far ahead like the old PG. And since the AI is more active, don't count on cities to be empty just because they were last time you played that scenario.
In the close fight you must prioritize the targets: AA, FA, AR (tanks), IN. Even taking the objectives and other units such as recon can be saved for later.
Use your FA to hit the AA. Then use a bomber to hit FA. If the battle is outside a city, hit the tanks next. If it is a city, hit the IN.
Now, if you have spare capacity, use additional bombers to finish off AA (it should be suppressed), finish off FA, then the tanks or IN. If you are hitting a city and the enemy is suppressed or has been bombed in some capacity, hit it with IN and mop up with tanks. If you have an armor clash on open terrain hold the IN back to guard the FA and AA while the tanks do the work.
This means you have a balanced force and you can do some task organization based on the sceanrio from your core force. You should have more on hand than allowed to be deployed but that is OK. You can use the strat bombers in big cities or when the sea is involved, more IN in big cities, mobile arty in fast moving scenarios like a raid, etc. You can always restart if you have the force mix wrong (nice option by the designers). Having a large balanced core and alternating units helps. By the end of '43 I have able to deploy: 6 tanks, 6 IN, 3 mobile and 3 self propelled (SP) FA, 3 SP AA, 1-2 88mm, 3 AT, 3 recon, 6 fighters, 6 bombers (mixed), and 1 strat bomber. I am rarely able to get most of them in the fight so you only overstrength the units you will use.
My probem with the AI is that it fights sort of dumb, rarely retreats, etc. Fighting smart usually wins when you have so many forces ahead of you. The AI has mass, so do not get strung out and take on more forces because your recon got too far ahead. Protect your bombers and mobile forces from surprise enemy air surges. That does not mean hovering over the ground units, use a spare AC and move ahead. Look for logical routes enemy air will come from and position along those routes. This is usually good at the beginning when your forces uncoil from the start/deployment locations. But as I stated, do not string out.
Speaking of deployment: I used to deploy FA forward so that I could fire from the very first turn. But if the AI gets the 1st move, then your FA is vulnerable. Watch those scenaiors, they are more frequent after '42 when the Soviets take more initiative. So deploy sometimes like it is a defense, you will not regret it. I often have more time than needed for the scenario, so take your time destroying the enemy properly.
Speaking of overstrength. I will do anything to keep my core forces experience. I wish you could strengthen your units 1 strength at a time, then you could mix some replacements with experienced replacements if you are really prestige starved. But, you can always disband units between scenarios, especially if they are captured equipment or even SE units that set your core out of balance. I doubt you need more than the 6 tanks but you could keep a 7th or 8th as a reserve and cash it in if you absolutely must.