should the size of polygons of a 3d model be the same? I recently learned from my previous question, that it's better make faces with 4 verts.
It really helped me with lots of things, unwraping, texturing, etc.
To reduce the poly counts of my models, I tried removing the unnecassary verts without turning any 4 vert face to n-gone.
But I don't know if it's OK from a professional perspective.
Please take a look at the image below.

M question is, can the polygons of a 3d model have different sizes? not slightly different, the difference between the size of the faces of my model is huge. i personally thought it's cool and fine but wanted to know some professionals opinion.
Thanks for reading my question,
Best regards.
You don't have to care about keeping the same size for all the quads, a topology doesn't need to be homogeneous, only bring edge loops when it's useful, delete all the ones that don't bring anything to the shape, you'll save calculation and your object will be easier to work.
For example look at this topology: You have small quads around the lips, they are bigger around the forehead, and even bigger around the shoulders, because it's exactly what's necessary for these parts, no more, no less.