What types of construction methods for circulation pipes are there in new multi-family residential buildings?

Good day. I would be interested to know which types of circulation pipe systems exist in apartment buildings. As far as I have already informed myself here, in the new construction of an apartment building (3 floors), a circulation pipe system must be installed. However, is there a "simple, cost-effective" variant and a "comfortable" variant? What is the difference? Are there regulations regarding which system must be installed? Thank you very much.

Only, there is a "simple, low-cost" variant and a "comfortable" variant.

Can you present both variants?

For me, a circulation line is simply another pipe with a pump that pumps the hot water back to the heating system.

Can you present both variants? For me, a circulation line is simply another pipe with a pump that pumps hot water back to the heating system.

One can, among other things, equip the circulation line with balancing valves or not. This way, the individual apartment circuits can be regulated better.

There is also the possibility to operate the hot water circulation by gravity, no pump no electricity.