(Disclaimer: I may be wrong, check with someone who knows the rules/has a rulebook/is ben)
-For fantasy WYSIWYG is not really enforced or a rule per se. Obviously if you take a character with a magical sword that is the greatest sword ever forged and you have your model with a wimpy dagger you might get some funny looks. And you're not expected to have your characters WYSIWYG because that would just be a pain in the ass. But for units typically you should have your unit modeled with the weapons they are using just for general purposes and sportsmanship. Like a unit of spearmen and your models have 2 hand weapons or something. It's mainly for clarity, like 40k, but not as strict or enforced.
Im not gonna say anything about line of sight really because I dont have a rulebook present and would most likely be giving you false information which I could have just done in my previous paragraph. Note the disclaimer...ahh screw it.
- LoS is generally you cant see through anything, units cannot see through other units, characters, warmachines, terrain(depending on classification), skirmishers, you get the point. Also you cannot see through skirmishers and skirmishers cannot see through other skirmishers if I recall correctly. The LoS rules go for shooting, moving, charging, and casting spells.
-There are a few exceptions such as flyers who can, once again have someone correct me if im wrong, charge over intervening units. Probably a few others but none come to mind.
-Hills do give you a height advantage letting you see over and units not on hills, but you still can't charge over your units or anything like that; the height advantage is mainly for shooting and casting LoS.