There really is not just ONE explanation for the trinity, or ONE explanation for Oneness. You'll find varying explanations from both camps.
There are dogmatic trinitarians just as there are dogmatic oneness people. Both sides can be eager to say that the other side is going to hell.
The majority of trinitarians that I have read, or talked to, are not tri-theistic. They will tell you emphatically that there is one God. They do believe that He has expressed Himself in three persons (although one trinitarian scholar that I read stated that 'persons' was probably not the best word to use). Oneness people use the word 'manifestations'. But if you talk to them, they often explain the godhead using the exact terms and explanations that we use.
I could never, ever accept that there is more than One God. But I'm also cautious in stating that all trinitarians believe in three gods. Because most that I've talked to don't. I've scratched my head a few times when listening to their explanations, because - hmmm.... that sounds like exactly what we believe!
Not all of them, but some. Particularly the more educated ones. This has just been my personal experience.
But then there are others.... yep. Three Gods. They are the ones that are waaaay off.