Don't edit the general BTS XML files. If they are already included in the BAT folders, then edit those. If they aren't included in the BAT folders, then copy them from the BTS folders (or Warlords or Vanilla Civ folders - depending on the file. Some aren't in the BTS folders), then edit them in the BAT folder. You never want to directly edit your Civ master files.
When you load a mod, the game reads first from the mod's folders to find any info that it needs. If it can't find the information that it needs to load, then it looks in the BTS folders, then Warlords, and then Vanilla Civ, until it finds what it needs. So as long as you put your changed files in the BAT folder, the game will read them before the regular BTS files, and it will ignore the regular BTS files as a result.
Also, get a good editing program like Notepad++. It's free and it's wonderful. You can get it here:
https://notepad-plus-plus.org/
BAT 4.1 does not change the AI at all. It subscribes to the BUG Mod mantra of not changing gameplay. However, BAT's sister mod, Better BAT AI, does improve the AI and still gives you all the goodness of BAT with an improved and smarter AI.
If you'd like to try it, the download link is in my sig. Enjoy!