I think Sobble explained the shapes thing already, but I got a little extra to add on!
Essentially, I like to think of the personality of my character and assign them a shape that I try to put onto their design. Each shape is associated with a different personality or vibe, which is related to Shape language. For example, boxes are associated with tough, heavy vibes, circles are soft and cute, and triangles are sharp and "untrustworthy" (this is very subjective, the specific vibe your shapes give will change based on the design! Squares don't have to be heavy and triangles don't have to be evil!!).
By combining your shapes, you can also combine vibes! for example, with my circle + square cat, I see them as a big soft grandparent-y fellow because of the big an' heavy vibe of the square and the soft vibe of the circle.
ahh I don't draw dogs a whole lot (since I don't have their anatomy down yet) so my dog examples aren't really my favourite but i hope this helps! lmk if anything is hard to understand ^^



