Now as to whether or not one is saved if they believe incorrectly here. I'm not sure, it depends on the type and degree of difference I'd suppose. I certainly wouldn't feel comfortable not accepting Trinitarian doctrine. As an example of type and degree of rejection, well some would say Krishna was Christ, and they're both just different modes of God. God is simply an elephant, and different religions are touching God in different areas/seeing different modes of existence to God. So if one is in fact embracing a plurality of religions leading to the same God (like various Hindu "holy ones" seem to do

In some instances, a denial of the Trinity will lead to Christ's divinity being torn, even Christ's own person. For example, if Christ is merely a representative mode of God, then the question must be asked who is one looking to for salvation? If Christ is merely a "mirage" of God then why do we worship and pray to an image and not God Himself? Or perhaps Christ wasn't God, but rather a special man sent by God. Now it seems evil of God to send a servant to die for us in order to have a relationship with Himself. Further still, why worship the creature (created) rather than the Creator?
So then, there are certain degrees and extents with which one can deny Trinitarian doctrine. The way in which one does could lead to rejecting Christ as Lord and God, even if it's not apparent to the person who is rejecting the Trinity.
Now, I'm not going to do all the writing myself, rather, this is just an introduction to a series of videos I found on YouTube from the InspiringPhilosophy fellow. He currently has a dozen videos on the Trinity covering what it is, how it formed historically, where such is found in the Old and New Testaments, its origins whether rooted in Paganism (polytheism) or Jewish monotheism. I'm sure others will find them invaluable, and I encourage a discussion after each one, people to challenge, ask questions and what-not. I'll leave a space of a couple of days or so between each new one.
The first video just looked at what the Trinity is. It is quite easy to explain the Trinity in a logical manner, more difficult is conceiving of Trinitarian examples. I'd encourage Christians to more focus on why we arose at the doctrine of the Trinity and the logic behind it, rather than trying to conceive of God as this or that -- because in our world while we see many things that represent who God is (love, goodness, righteous, forgiving, merciful), there are perhaps zero things that adequately represent what God is (Cerberus the three-headed dog, ice-water-vapour, etc). So now, the first video just looks to logically define what the Trinity is.
Video #1: What is the Trinity?
https://www.youtube.com/watch?v=1gCv-FAjgps