it all depends on playstyle but see thats a contradiction as if you're playing soviets you can do a 5 or 7 conscript epening which allows you to have sqauds in groups of two if i have two us rifle swauds together it means the rest of the map im open except my third rifle squad or rear echelon squad i think as U.S. you do have to be much more tactful and intelligent about when and where your troops encounter the enemy and on what terms while not letting the enemy walk all over you. im certainly far from the best though i find as us im always playing catch up and teching to late
I always buy an extra RE at the start, then 4 rifles followed by teching what needs to be teched.
Send the RE's capping opposite ends, send your first rifle in the middle, the next 3 rifles then go to where the enemy is. If you see an engie squad you know that he isn't focusing there (well, 9/10 at least) and his main force is at the other side of the map.
The 2 RE opening gives you a lot of map control fast and the 4 squads of rifles make it really easy to lock down 1 half whilst you attack the other, reducing their map control further. It's a lot of Micro and a god awful lot of concentration (especially if you tech LT AND CPT) not to lose a squad.
I would dare say having 4 rifles is more important than teching at the first chance you get, and keeping 4 rifles (replacing if a loss occurs) is vital.