With the way Soulframe is structured, our Envoy as of now is a self-insert. You can customize their looks, their virtues, their gear, they are you. However, it becomes harder to self-insert the more your character talks and does things that you wouldn't do. This is actually an issue I had with Warframe, as the Drifter and Operator would always say things I'd never ask them to say.
Ultimately, DE needs to decide if the Envoy is our character or theirs. Depending on how they approach that will determine how important the decision for voice acting is. And the most questionable aspect then becomes how well written the player character will be going forward, as voice work will change that aspect dramatically, in both ways. I believe that a silent protagonist is best for a game where the character is your own, as this allows the player to fill in the gaps with their imagination and focus on reading the context clues. A vocal protagonist would be best if the devs have a specific character in mind and don't want the player to self insert. It's all about who the Envoy is written for.