Dwarven Warshields are explicitly listed as a shield in the source material. Thus any feat that applies to generic shields or generic weapons would apply.
It is unclear as to whether or not they are light or heavy unless I've missed an errata somewhere, in the event that this is an important distinction.
In my game, my character's dwarven warshield is being treated as a light shield, partially due to the +1 shield bonus and partially due to the rule that a weapon that provides a shield bonus is treated as a light shield.
https://www.d20pfsrd.com/equipment/weapons/
Shield (1 DP): The weapon counts as a light shield made of wood or metal and can have armor spikes (your choice). Add the gp price of the shield and any armor spikes that the weapon gains from this quality to the weapon’s gp price. This quality can be added only to one-handed melee weapons.