The issue comes from the walkthrough mod, specifically the fact that there isn't enough room to fit all the options once the mod adds an extra line to show all the stat changes. The menu is supposed to look like this:
View attachment 3031965
The easiest solution is to save the game on that screen then open the save in an unmodded copy of the game, select Charles, save the game after making the choice, then reopen the modded version and load second save. You'll be on Charles' path and should be able to play normally after that. It's a little cumbersome, but it does work.
The ideal solution would be for
JokerLeader to adjust the mod to address the issue, but I'm not sure how easy that would be.