How do combats work

I'm not very familiar with 4X gameplay in general, but some aspects of the battles remain quite unclear to me. The following questions are about manual battles. Quoting the user's guide:

Battlefield and positioning

An important element […] is that they take place directly on the Adventure Map, not on an abstract battlefield. When you decide to attack an enemy army, you should choose the location of the battle carefully to take advantage of terrain opportunities: Altitude may grant you a bonus, and cliffs can prevent enemy units from reaching you.

How do you choose that location, exactly ? Should I attack opponents from the side of their tile that will push me on the most valuable direction/area (for instance, west cliffs for my archers) ? Is it possible to get a preview of what the battle area will be when engaging before actually engaging an enemy ?

Also, it can happen that more than 2 armies get engaged in a battle. I think it's simply because when the effective battlefield spreads out, more than one army stands on it. Once again: is it possible to get a preview of this area before engaging ? Are those extra armies the "reinforcements" mentioned in the guide ?

4. Some units (greyed out) are placed in reserve and will enter the battle as reinforcements.

Turns

I was expecting a turn based combat system. Turns out that it doesn't exactly work that way: once the resolution phase has started, each unit act for more than one turn and will eventually stop after 2 or 3 turns. Is it normal ? All the guide says about it is:

Depending on the game settings, the battle can span several Order and Resolution phases. Once these phases have completed, the battle ends.

Should I change something somewhere in order to have "normal" one-by-one turn gameplay ?

Ranged attacks

Where can I find the range of my ranged weapons ? Is it possible to preview it during deployment or order phase ?