FWIW, I think that both lines in question should stay as they are.
“It was I who bridged your minds.”
Snoke bridging their minds could honestly be a jump start of something that was going to happen anyways or a lie. And either is a fine enough explanation.
“I have been every voice you have ever heard inside your head.”
Palpatine has been manipulating Ben Solo from Exegol through Snoke (either as a meat puppet or a servant and it doesn’t matter which) and through the legacy of Vader. Either through Vader’s voice or visions from the helmet or simply through the history that’s there. “It has been I who has manipulated you through my influence with Snoke and Vader.”