What do you do if you have engineers on a project who each prefer a different style?

Fight it out decide on a common style and stick to it. And also decide which issues are worth enforcing. In other words; (much of) the spacing issues you describe above are clearly very minor, and for minor issues the rule should probably be: don't change what's there unless you're doing actual work on the code involved. That should at least keep people from committing thousands of lines of irrelevant changes back and forth.