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Here, it largely depends on the situation:
The positioning of archers depends on the speed of the enemy units and the speed of the units in your army (if your army has units with the same speed, it depends on who should move first, especially if their turns are mixed with the enemy's).
Example: playing as the Swamp faction – Lizardmen, Vasas, and Hydras have a speed of 5 (the hero isn't specialized). The opponent (or neutral creatures) also has archers with a speed of 5. If it comes down to a ranged battle, it's desirable for the Lizardmen to shoot first, so they should be placed on top so that they move before the Vasas and Hydras. This is just an example; everything, of course, depends on the situation on the battlefield. (This, by the way, applies not only to archers but also to melee units: this is a separate topic about the order of turns).
P.S. Of course, in any case, if the battle isn't decided in 1-2 rounds, you need melee units to provide cover; in this case, top vs. bottom positioning doesn't matter.
P.P.S. Regarding the group stack of neutral creatures, again, it depends on the speed of the neutral creatures. If you can eliminate them all with ranged attacks, then, of course, it's better to place the archers at the bottom, eliminating the group stack first, and then the rest. If you can't eliminate the group stack, then it's better to do the opposite: place the archers on top and reduce their numbers, and finish off the rest with melee units, although again, this depends on the speed of the neutral creatures; sometimes, it's better to place them at the bottom and eliminate the fast ones (i.e., the group) while the slow ones haven't reached you, and then it will be the slow ones' turn. Again, it depends on the situation: is there an opportunity (or a need) to slow down/distract (or spread out) some stack? A ballista can also distract.
In general, there's no single recommendation: in each individual situation, you need to calculate separately – look at the speed of the units... something like that.
P.P.P.S. A poll in this form doesn't make sense, in my opinion.