Playing as the Stronghold faction (Disciples 2).

Similarly to the post about demons, everything depends on the opponent and the map.

Good! And if you have 3 opponents, what would you do?
It's much easier to choose the right army when playing 1vs1 than when playing against 3 opponents at once.
On a small map, when playing against elves, you can confidently choose Templars instead of Skeletons. Why? Because there is a high probability that the elf will expect you to counter his archers, i.e., something with weapon immunity. And, following this assumption, he will focus on Elemental Archers and, perhaps, even mages. And what will his surprise be when he sees Templars? :)

I absolutely do not recommend focusing on mages against elves - this is a defeat in 99% of cases. The best option is a Dragon and Templars.
As an option, on a small map against elves: Warrior Hero + Dragon + Templar - this is at the start. Later, add a Shadow (paralysis, level 3) to them. If the map is not very small, and there is an opportunity to develop the hero to level 6, then take another Shadow. Believe me, even with a level 2 Dragon + Warrior Hero + Templar + 2 Shadows, the elf will have a very hard time.

Against humans on a small map, a good option would be: Warrior Hero + Dragon + Adept - this is at the start. Upgrade the Adept to a Spirit, and after gaining another leadership point, take either another mage - if the opponent is developing Inquisitors, or a Shadow - if the opponent is developing Knights. Upgrade the Spirits to Spectres.
This option is good because at the start, we have only 3 units in our army, so there will be more experience. Why Spectres and not Skeletons? Because if the human is developing mages + Patriarchs, with Spectres, which have an initiative of 50!, we can make our move before the mages. Consequently, we will lower the level of the mages, which will reduce the damage they deal to us. Also, Patriarchs can only resurrect at level 4, so by lowering their level, we deprive them of this ability.

Against demons, it's more difficult... Again, when playing on a small map, a skilled demon will develop Gargoyles, as the elf might be wary of weapon immunity. A good option would be: Warrior Hero + Shadow + 2 Adepts; later, after gaining another leadership point + Templar. Upgrade the Adepts to Spectres if the demon has Gargoyles. If the demon does not have Gargoyles, then upgrade the Adepts to Skeletons. As an option, it might be a good choice to develop Adepts into Liches, but it's not certain that you will have enough experience, and you will hardly be able to do anything to the demon with Necromancers.