Could you please share a bit more about your scenario? Do you want to remove a user from these selected values/options within the Multiple Choice People filed? Or exclude the user when select a value/option within the Multiple Choice People filed (exclude the user from available options)?
Further, do you want to achieve your needs within PowerApps?
I have made a test on my side, I afraid that there is no way to achieve your needs in PowerApps currently.
Community Support Team _ Kris Dai If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.