I have tried (Soviet) platoons of 3 elements, one with SMG+LMG, 2 with rifle+LMG.
However, I soon came to the opinion that 3xRifle+LMG works best. In order to use the hitting power of the SMG means that you have to walk through 6+ hexes of rifle fire in order to get close, unless you can reduce visibility that down with smoke, city grid, shell fire or whatever. Defensively, the mix is better, since you can ambush inside woods, or behind a ridge line etc.
Mixed within a platoon works best since then there are 2 rifle elements right by your sub gunners able to reach out and touch enemy riflemen if required. An isolated SMG-only platoon tends to melt under long range rifle fires. Especially against a human opponent who will recognise their range limitation and refuse to close. (AI may well advance on them of course!
).
AKS, or even SKS carbines (at a pinch) are miles better than sub guns. Bolt rifles are better than SKS.
In the real world there were never any "trucks as APC" type platoons. Exceptions would be the UK WW2 motor bn, and some German WW2 ones - with a 15cwt light truck per section. However, those would tend to deliver the troops to about 1000-1500m, and then retire to lager while the riflemen walked the last bit. So only a mobility assist,
not a substitute APC.
Medium trucks used to transport infantry would come from accumulating the battalion and brigade logistical assets (after first emptying those of the immediate rations, ammo etc reserves). Such an accumulation of trucks would be used to shuttle a brigade's companies forwards one at a time for 10-15 miles as a taxi service. Troops would be dropped off
well away from the contact line (miles) - and the taxi service would go back and fetch the next company. So, only used for behind the lines administrative deployment. Medium or larger trucks were simply too valuable to lose by using as "APC".
( Old fart mode on : I recall doing a similar "shuffle taxi" on the Bn trucks as an overnight approach, Bn assembling on a kick-off line about a mile off the target and doing a dawn assault on Salisbury Plain back in the 70s. Oh such sheer joy! - it was
up an iron age hill-fort at the very end, and muggins was carrying the platoon backpack radio
!)
Therefore, in a core, unless it is a British motor battalion or similar rare "organic" light-truck organisation, the only trucks I have are the weapons carriers in e.g. the mortar and AT platoons.
Trucks in the core will gain experience, so become more valuable points-wise, just like any other troops.
But the experience will gain you nothing since they have no combat ability. Maybe be able to pull off a rally when needed, is all. All the extra points
will do is make the enemy forces stronger over time, as the non-fighting soft-skins accumulate in value. In addition you will be spending a lot of repair points fixing them when they inevitably get bent.
Therefore my Soviet cores in WW2 or early post war always work as leg infantry. Occasionally I might buy a truck formation to act as taxis if the map is conducive to the buy. But I am always super cautious, since trucks packed with troops on a road are mortar magnets, IMHO. Guaranteed customers for the local A&E department, really. Cheap but cheerful tin-can APC are better for the shuttle service as and when available.
Also I usually use the tank co to lift an advance guard leg infantry co up towards the front. I might manage to use the tanks to taxi up two rifle coys before any contact happens.
Once decent usable APC (Which I classify as the BTR-60P with its 14.5mm turret) arrive, then I give up on leg grunts and go for the doctrinal 3x BTR-60 coys and 1x14 tank support coy. I find BMP are too expensive really (different case if say Egyptians on open desert maps). The 14.5mm deals with any NATO box-on-tracks APC with rifle calibre MG just fine.
Cheers
Andy