In what blocks could mobs spawn?

According to the wiki, mobs do not spawn in water or lava, or in a block that has higher light level than the limit for the respective type of a mob. However, it appears that mobs also cannot spawn in pressure plates, and that seems like a an exception to me, since pressure plates aren't solid.

Are there any other non-solid blocks that prevent mobs from spawning in them (not on them)?

Solution 1:

Yes, all the blocks that are non-full and have a hitbox that touches the bounding box of the mobs will prevent mobs from spawning in them. This includes Carpets, Slabs, Stairs, Daylight Sensors, Redstone Repeaters, etc. As an exception (as you said) Pressure Plates also prevent mobs from spawning, maybe in order to make mob spawning harder, but this was not the case before the Minecraft 1.9 version.
They will spawn in most non-solid blocks, regardless of being full or not. This include Grass, Flowers, Sugar Cane, etc.