No you don't know where the bombs, teslas, giant bombs and traps are. It is still time consuming, creating the base and trying your attacks. And yes you can try and copy your opponent base and attack it until you get it perfect.
It is called training

. All blacks train for their games, soccer team train for their games, a runner train for the marathon, even though they roughly know who their opponents are. There is also the day of the performance: if you wrong because under pressure you are not going to get 3 stars anyway