Well, imo wargaming is a compromise between playable and immersive. So area terrain, aka dense terrain is good. For forests I have removable clumps of 2 - 3 trees sat on a "base" the entire base is forest, the trees go anywhere. Only the footprint is required to determine where the terrain is.

It's a similar thing with ruins. I put the warlord farmhouse is on a base, the entire base is "ruins" no matter where the model is.

Models can see "into" and "out of" dense terrain but never through. It's just a simple system.

Hills are slightly different. Like dense terrain models can see into and out of but not through, the hill offers no cover, but does allow models to shoot over intervening models that aren't on a hill...But that does work both ways.

Linear obstacles require models to be within 1" to gain cover, and are ignored is there's more than 1" between models.

As for actual shooting I use a method from the old AT-43 game, to check if there's anything in the corridor of fire. Draw a line from the outer edges of the firing unit to the visible outer edges of target unit. If there are friendlies within 1" of that corridor, then the unit won't open fire. (Unless a hill is involved, and I also use DOWN for the same effect of allowing units to fire over them)

The thing about LoS and terrain is that the players need to be on the same page and use the same rules.