Not sure about a stand-in cast, I compared new Aerith to Crisis Core Aerith and I think they're the same actress - Andrea Bowen. I also think Cloud sounds about right compared with Crisis Core.

In terms of sound of the acting sounding a bit sketchy... yah, that's English Final Fantasy in a nutshell! They haven't had a non-sketchy one since XII. Overall, looks good! Last year or so I'd got into the 'lol FFVIIR is such a joke' phase but this has restored some of the magic I felt at the 2015 announcement. Shame the UI showed Tifa a bunch of times but she didn't actually appear in the trailer ¬_¬