I rather my users only able to modify theirs own topic title than anyone. How do I do this?
Turn the requirements for TL3 up so high that nobody can reach them.
What if you want users to be able to do everything else TL3 allows? Modifying titles/categories is the only TL3 permission that “affects others directly”. Everything else (more likes, stronger flags, access to lounge, etc.) is generally transparent to others.
Not possible at this time, and not planned.