You generally won't have any value for an ICML submission even if you are the 1st author, however, being a co author for an accepted ICML paper always counts. It should also improve your LOR. Regarding EMNLP, 3rd author would add some value if it's a long paper. For short a paper it's of little value IMHO. Again the paper should be accepted, 0 value for submitted and rejected papars.

I have seen many people putting reviewing as a service in their resume, also some conferences allow you to be reviewer if you are one of the co-authors, thus hints at your credibility to be a part of such conferences. Finally reviewing also helps build a better profile for visa and all, if you are in the USA as an immigrant.