I was making an elven list for my friend for tournament and i came up with a idea of Elven Formation.

This list involves Deepwood Archers at the centre (D), two 1x3 Lenox riders (L) and two 1x3 Ventala Skirmishers (V) (yes, i kniw they arent released yet but idea came to my mind when i've put two 1x3 lenox riders units into the list) whole concept works around mobility and speed. Archers form a solid centre with Lenox and ventala turning to the flanks. Whole strategy is based on keeping ventala just one base ahead of lenox to allow them to fire while lenox act like a shield that moves togeather with our centaurs and in crutial momrnt they can turn in on both flanks to engage potential threat. Do you deploy your troops in formation or just basicly counterdepoly and try to pick the best matchups possible (like deploying cavalry in front of archer block and try to force that fight)

Terrain could really interrupt this I would think.

it depends where exacly would you put this army. you could spead lenox ventala units further away to avoid terrain

I play Daqan, and my favourite units are basically self-sufficient so I'm a pretty bad example, but I deploy units quite independently, with the notable exception of a Rune Golem to intercept for my Crossbowmen. I think in general ranged units will need more support, especially in Waiqar where blight application can be so important, but terrain and enemy deployment is too crucial to go into a game with a plan as specific as this one. Now, treating each pair of Leonx/Ventala as a mutually supportive team could sure be cool, but you've gotta stay versatile.

other idea i came up with is daqan defensive formation with 2 units of 3x1 crossbows and 3 2x1 units of spearmen that form a shield wall right before crossbowmen (and this could also work with golems or carrions or pretty much any unit and i believe many players use it in some way (by putting single tray in front of big shooting block) .

Also deployment in formations could have its advantage fr9m just counterdeploying because your units can be fighting in a way that they suport eachother. Question is: Is there a formation strong enough that makes it worth above counter deploying.

Terrain definitely affects deployments, but (perhaps unsurprisingly) the deployment card can drastically effect setup. My favorite was playing Careful Approach in Store Championships. We both elected to put our terrain along one long edge of the board, so the middle was wide open. My deployment looked like this:

After unpacking my units, including wheels by my Reaimates and my not-yet-fully-painted Reanimate Archers, my deployment looked like this (at the end of round 2, I believe):

I think using wheels and minding your initiative values can really help you start off in an odd configuration, and then spread out to become a major threat. This formation was for the objective "Demoralize Their Forces", and although I just sort of came up with the idea on the fly, the goal was pretty obvious: protect my archers while at the same time protecting my flanks. I barely scraped a win, but it was a tense and very fun match!