While “un point c’est tout” is usually an assertion of authority (you have the “power” to shut down furtehr protest) or independance (you can afford to ignore anything further the other person might saying), et toc! is a put down.

Basically et toc! is a barefaced and insulting assertion of dominance. There’s not really any reason to add “un point c’est tout” there (at least to me): it just means something like “and that’s final” (i.e. “end of discussion!”).

“un point c’est tout” is added by someone who just spoke to say “full stop, I don’t want any further argument about this.”
“et toc” is said by someone who listens to other people’s talk or the like to mean “he got him/them, well said, good point …” or something similar. I take it as the noise of an arrow or stab hitting its target. It was a more frequent expression some 30-40 years ago. Not to be confused with “toc toc” which means “knock on door” (knuckle on it) or “foolish” (finger on temple), giving in some regions the verb “toquer” (knock on door) and “toqué” (past participle “knocked” or adjective “fool”).