To e-collar or not

We have a 1 year old, intact male who we're having some behavioral problems with (growling at visitors, resource guarding our couch, etc.). We've tried general training with treats but now he only listens if we have treats. He's gotten better not reacting to dogs walking by on walks (we don't let him sniff), but the people uncertainty has gotten worse. I'm worried to have friends over or let anyone pet him. My question is, what are your thoughts on e-collar training. I went to a trainer who wants to use one and I even felt the vibration, it wasn't painful at all. But I've hear e-collars can cause emotional damage to Mals. Thoughts? Also, tbh, if we don't do the e-collar training, we're rehoming him to a sled dog place in Michigan...

Edit: we are not doing the e-collar ourselves. It would be at a boarding training school first for 10 days. Then we’d learn to use it correctly.