Are mindflayers much nerfed on 5e? Because on BG2 i had problem dealing with then with high level party members. How they plan to have a low level game with such powerful creatures?
Since intellect devourers are CR7 creatures that are considered by most DMs as party killers and in the gameplay, a party of two just killed three of them easily (and the Intellect devourers did not use any of the nasty psionic powers they have and made them very dangerous in PNP) I will assume that many creatures are de-levelled and nerfed in BG3 (The devs announced that the game will have a level cap of 10).
https://www.5esrd.com/gamemastering...type/aberrations/intellect-devourer-3pp/