You can change a database’s name by going into the database editor and clicking the name in the upper-left.
Wikis are basically pre-made lists of entries in the respective category that you can search through when adding items to your course. The most useful thing to me about using one was being able to import mems that had been previously made for those entries. Furthermore, any mems that were later made in your course would also show up in other courses that had imported that same entry.
However, they removed this feature a while ago, so mems are no longer imported when using entries from the wiki. Audio and alts are also imported sometimes, but I more often than not ended up replacing them with my own, so I have since stopped using the wikis altogether.
Going by this post, I wouldn’t expect wikis to stick around at all much longer anyway, personally.