<<Is Delta pretty strict with their rules? >>
No, they are absolutely fine - as long as you stick to their rules.
Even if 1000s of people told you that they had had no problem with their luggage being slightly over the weight limit and slightly over the max dimensions limit, do you really think that it would make any difference if you were confronted at check-in by someone who insists on sticking to the rules?
No, of course it wouldn't.
That super-excitement may become a little jaded if your case is rejected because of size or you are charged extra for an over-weight case.