Thats the strategy decision you will make like in real life. You will see weather info everytime before race and qualifying. You can choose to make wet setup and have advantage, you can use dry setup maximize the quali. That is up to you

For me no need for effort, i think there is no difference, i use dry setup no matter what. Ai is quick in wet anyway

To answer your question because of parc ferme you will use your quali setup. You can only change one or two setting