You need the alpha for each layer and then either blend the layers directly or use a landscape-blending node. The manual blend is on the left:
As far as texture objects vs other texture-type-nodes the Object node is ‘just’ a reference to a particular texture. You likely need to actually plug it into a Texture SAMPLER to actually sample a pixel. The sampler nodes are what you set to “shared:wrap” so they don’t consume as many sampler-slots (they are limited!).
I’d recommend this guy’s course on landscapes, it’s what got me started: Landscape Material Tutorial Part 1 (Unreal Engine 4) - YouTube