Okay, in modding the term "vanilla" refers to the unaltered, original game files, i.e. what you usually start with when making a mod.
Now to TSLPatcher: You must have noticed that many mods, including those two you posted above, come with a .exe file that's usually called TSLPatcher.exe. What is that and why does it exist? Let's start with the latter.
For that let's assume that two mods alter appearance.2da as an example. Let's say one of them changes Mission's look and the other one changes Bastila's look. If both of those simply provided their modified appearance.2da file, you cannot use them together unless you're a modder and know how to merge them. That was the case in the very early days of KotOR modding. But lucky for us, stoffe developed a tool called TSLPatcher that fixes these incompabilities.
How is that done? It's really simple actually: Instead of providing the modified appearance.2da file, you provide a .txt file (called changes.txt) in a folder calles "tslpatchdata" together with the TSLPatcher.exe. When the user runs TSLPatcher.exe, it will look for changes.txt and apply these changes to the corresponding files in the game's Override folder. So now if two mods modify the same .2da file, they won't conflict anylonger as they simply apply their changes to the same file, thus merging the mods.
There's a little more to it: What if the file to be modified doesn't exist in the user's Override folder? Then it couldn't be modified. This is why a vanilla copy of that file is also placed in the tslpatchdata folder and TSLPatcher is told to copy this to the Override, unless a file of the same name is already present. Then the changes will be applied. So either TSLPatcher applies those changes to the already existing and most likely modded file in the Override or to a fresh vanilla file copied there.
This is why you NEVER copy the files from tslpatchdata to the Override. Mods simply won't work then, as they require the changes done by TSLPatcher. The same is true in your case: spells.2da is a commonly modified file, so instead of providing the modified files, the two authors of the mods you posted, use TSLPatcher. That's why the spells.2da files in the mod archives do not list the new force powers. Those are vanilla files. Only when properly installing the mod by running TSLPatcher.exe, these new rows will be added to the spells.2da in the Override folder. This is why you have to install the mods first, before you can make changes to them (or you make these changes in changes.txt but I wouldn't recommend that).
This is also why there's no work required to make them compatible. You install both of them and thanks to TSLPatcher they will work together. Then you can of course apply your desired changes afterwards, but manually making them compatible is not necessary.