Kuo-Toas aren't specifically mind flayer minions, but they were in bg2 during a particular part of the game where you encounter mind flares. So, it would be a nice throwback to include them at the beginning of bg3. Besides that, they are a CR 1/4, meaning that you could have four...
Now that you’ve made your way atop the Netherbrain, you’ll need to have your mind flayer make their way up to the Crown of Karsus andcast Karsus’ Compulsionto dominate the Netherbrain. The rest of your party will have to contend with a group of mind flayers, some grabby tentacles, ...