Download
WinMerge, and go through the folders first, and find which files are "different". Open WinMerge, click on the "File... Open...", and it brings up a dialog box with a "Left" and a "Right", and "Filter". Be sure you've got the little tick-box for "Include SubFolders" checked. Click on the "Browse" button for the Left, and load a folder or file you want to compare. Click on the "Browse" button and pick the same location in another mod. Click on the "OK" button, and see what happens. Hopefully, you get a window with a tally of the files found, if you're comparing folders, and side-by-side text boxes if you're comparing files. Easy-peasy, sort-of... You do have to be careful of file edits, since on mine, it might skip a whole section of a file, and just try to match "[Heading]" numbers for some reason, instead of matching the text under the headings. In cases such as those, you can select the side you want, and edit "by hand" if necessary, including selecting and copying text from one side, and pasting it to the other side. You use the <Alt> key in conjuction with the <Arrow> keys to move from one marker to the next (<Up> and <Down>), and to move text from one side to the other (<Left> and <Right>). If you can't get the hang of it and can week several weeks, I might have things quieted down here, or maybe someone else could help you with it...
btw - DO
NOT do edits of binary files, such as DAT, in the program... you will trash the file...