In Annihilation, Troops are just another unit that can become a kill point by dying and generate kill points for killing other units. In most cases, Troops choices are less effective at killing and as easy or easier to kill than similar Elite, Heavy, and Fast Attack units. This is obviously an overgeneralization, but it matches the game design and is more accurate than inaccurate as a general rule. So in Annihilation, fewer Troops choices are better for most armies. The exceptions include Chaos Space Marines Cult Troops - Khorne Berserkers are very killy, Plague Marines are among the most durable, Noise Marines produce significant Dakka, and Thousand Sons have great antipersonnel fire and are the best unit to take Demolisher cannon hits on. Dark Eldar should generally take a maximum number of Troops, as they are a bargain for their killing power. Imperial Guard can go with a large number of Troops, especially if they have a Platoon that collapses into a Commissariat Blob. Yes, you can mount the platoon squads in Chimeras, but blobbing 30+ in Annihilation makes the unit essentially nonviable as a kill point for most armies.
In Capture and Control, most armies really only need two scoring units, as there are only two possible objectives. Reserving a unit to hold your own objective at the end of the game and sending another towards the enemy objective (often obliquely – no sense trying to hold an objective against counter attacks for 3 turns) is generally a good default behavior. If you are Eldar, you need at least two units assigned to each job, as Wave Serpents break down at the most inconvenient times, and walking Eldar Troops aren’t known for their durability. Guardsmen need more units for defense (and possibly offense, but Guard should focus on eliminating all enemy scoring units and/or contesting the far objective, in most cases) – I like 3 units in the area to hold my home objective, and I tend to devote the rest of my Guard force to immobilizing and then eliminating enemy contesting and capturing units. Space Marines often do well to Combat Squad a couple of units for home defense, working on the premise that killing two units is harder than killing one.
Seize Ground can have up to 5 objectives – so obviously you need at least 5 scoring units, right? No, not at all. In almost no cases should you be able to take more than 3 objectives – your opponent has to be really asleep for you to get to 4, and if you’re looking at 5 objectives, just go ahead and go for Wipeout instead.
Seize Ground is the mission designed for Space Marines. Combat squads mean that 6 scoring units are very likely for most Space Marine players, and each unit essentially has to be destroyed totally to be stopped. Eldar also love Seize Ground; mobility is really all they have going for them, so having a lot of objectives to hope to tank shock a Wave Serpent of Dire Avengers onto is a very good thing.
From the articles I take away the following concepts.
1. You don't need to contest all objectives, just the majority of them. If there are five objectives, you need to take 3 to win.
2. Troop choices need to be protected. They need to survive till the end of the game. There are several ways to do so. Firstly shield them in terrains. Secondly take either large units that are hard to reduce to less than half, or make them particularly resilient.
3. One to two troop choice should be mobile, held in "reserve" until toward the end of the game when they can rush forward and take an objective.
4. This means minimum of 3 troops and maximum of 4 troops.
5. Other force selections, whether it be HQ, elites, fast, or heavies should be taken to attack, and they really should focus their attacks on enemy troops as much as they can.