For ripple effect usually common way to do was create a mesh and modifier into a circle shape, so the uv maintain square, but you’ll need a lot increase a lot faces to achieve smooth looking.
That i try using shader to achieve similar technic , and the result was surprisingly good. Smooth face and no need mesh to achieve it.
I thought the most common technique was using polar coordiantes of the texture with shader, I would never thought creating mesh would be the no. 1 technique 
its either/or.
both have their uses 
Using a disc mesh would help reducing overdraw but adding thickness to geometry, so it has pros and cons.
im sorry i not a technical artist, when i search all the tutorial, basically they would use a mesh to achieve it.
i think is because using mesh is more direct and easy understand, also have more flexible.
using shader to achieve it have their limitation.
Shader is hard 
Yea, still you can use a dithering to reduce overdraw issues, even as a shader it will be pretty performant
No worries! Exploration is always great, it always better to know how to make similar stuff with a different ways! Keep going