1. If I change the Title Boost setting, should I recreate an index?
   
2. Can I prioritize an app in the search? Example: we have articles with exact search term in the title, but these articles are displayed below the forum posts and entries that even do not contain searched term in the title. I would like to have articles first if they have exact match, as they contain everything to the searched term in a structured way. 

1. Well, if you change anything that requires rebuilding the index, it will happen automatically or you'll be prompted to do it. As I recall, you do not need to rebuild the index to change those values you highlighted.

2. There is no built in capacity at this time to accomplish what you are asking about, however it is doable at a technical level so it could be developed as a plugin in theory.