https://drive.google.com/file/d/1MU_GV9F4liloikJwDsxjMK1NEvfKnz4q/view?usp=sharing

Michael, firstly thank you reply.
I attached the most primitive example - 2 perpendicular cylinders with a fillet; plus some screenshots from max+vantage (but it'd look bad in any render engine - **the long perpendicular triangles are almost 90 degree to adjacent faces!**).
Trying pour more poly count is a bad idea - it really doesn't solve it. The mesh should look decent even in lower poly count.
Again, I can solve it by playing with aspect ratio limit slider but it adds unnecessary poly count (in some fields like archviz its crucial to stay lightweight)