"you will consume same amount of trafic. Async or Sync it's related to time of execution"

Correct, if you're querying external APIs; however, in this example, the same API is querying itself.

"you can be banned in case of passing the limit rate of requests to specific api / page"

This is a very good 'con' that I didn't address! If making queries to/from the same API, it could be subject to its own authorization limits.

Good call outs, man. Thanks!