These DDT files cover the Top 2 (Top 4 in England and Top 3 in a couple of nations) leagues loading players in from these nations and also increasing the likelyhood that regens spawn from nations not loaded in. The total amount of players that the files load in is about 80-90k if you have a large DB selected with the files. The game speed is still really fast for me (for reference i have an i7-3770) and i can blitz through seasons with ease.
How to install:
1.Extract the zip file
2.Navigate to your FM Touch install folder
3.Copy the extracted folder "ddt" to all of the 21xx folders that are in "Football Manager 2021 Touch\data\database\db\"