I want to install two led strips in a large sitting room mainly for the audioreactive ussermod. I have already finished the first led strip with a max9814 mic module and it works as expected 
. The other led strip will be 7 (or more) meters away. I am considering of building another similar ESP32 module and sync it to the first one. If I do this will the sync send the data as well via the wifi or should I add a mic module as well to the second ESP 32?
I think the answer is yes.
yes - I need a second mic module as well or
yes - sync transmits data to the slave esp32?
syncs data over wifi.
I think I read that when I set up my first one.
Sync will only make the other device play the same effect. It won’t send the mic data over WiFi.
However, you can add the 2nd wled device as a DDP networked strip. The setting is in LED preferences. That should do what you want. (Click the plus button and then change type in the drop-down to DDP RGB(W).)
You can also sync audio data.
what configuration is required to sync audio data? The DDP RGB mentrioned above?
Check the usermod settings.