Does deferring admissions to PhD affect future (post-PhD) career path?
In general, there is very little effect from taking a year off between undergraduate and doctoral studies, so long as you complete your graduate studies in a "normal" manner. The primary concern is how you did as a graduate student on your particular project; after you've received the PhD, the particulars of how you got there are much less important in determining your future career path. There may be some people who are prejudiced against people who deviated from what they consider a "normal" trajectory, but I wouldn't expect this to be a major fraction of potential employers. (And more to the point, you probably wouldn't want to work for such an individual anyways.)