Our company website shows most men in a suit and open shirt, that was requested when we had photos done. Day to day we dress down apart from meetings, external events etc.
As a hiring manager I would be a bit surprised to see a man turn up for interview in anything other than suit, shirt and tie. A three piece suit wouldn't be necessary. I think trousers, shirt and blazer would be ok, especially if someone normally works from home or in an area where more casual dress is common.
Suit with an open neck shirt would look a bit lacking effort/care. Just because a tie is so easy to add, low cost and not size dependent.
Trousers, shirt and tie, or trousers and open neck shirt seems a bit under dressed unless it is a school leaver, or an interview for a role that would normally wear uniform or casual wear.
I think you should always dress more smartly for interview than you would expect to dress for the role day to day. I would wear a suit myself for an interview.
That said, dress is a minor point, we recently recruited someone who both interviewers thought was a bit casual/scruffy for interview but was a better candidate than the one in a suit. If it is close though it can make a difference.