For me, partly it depends on pool levels. Constantly checking that, and assigning the stuff that is plentiful. For example you might have a lot of 122m howitzers, but low on 152s.
All infantry armies get artillery (several battalions/regiments), heavy and light AAA, a sapper unit or RR construction unit and once the pools are sufficient they will get at least one armor battalion/brigade. Some get flame tanks, but these tend to be scarce. Once assault gun formations are available these get used too. Again, it's shaped by what is available at the time.
As the war moves on I tend to have a huge stockpile of katyushas, and those begin to be used heavily, essentially replacing the tube artillery.
For armor units (tank armies/shock armies) I forgo the heavy AAA and heavy artillery. These get a standard/heavy tank regiment/battalion/brigade (depending on pools), light AAA, and plenty of rockets. Always concerned about trucks, so I keep support units attached to these formations streamlined.
In 1941 I concentrate on diggers, AAA and artillery. Once the blitzkrieg has been stopped, and production stabilized and running full tilt, I begin to incorporate the armor support units.
I tend to ignore ski battalions, MG units, AT guns and mortars.
Edit: You're asking about Corps, so perhaps I answered the wrong question? You're an experienced player and I doubt you need the advice I just gave.
Pretty much mu outlook on armies, and yes it was Corps I was asking info on.
I guess I am in trouble then since I have not adhered to this way of thinking. I have disbanded all of my AA guns for manpower netting about 120,000+ men in 1941. I have assigned AT guns, MG Battalions, and Motorcycle regiments to my Corps :( I have almost completed having every Army on the map having 5-6 Artillery units. As for the Sappers I have them assigned out but their bang for the buck has been diminished.
Space we can recover; time never