When it is written that “God is not a respecter of persons,”1 it means that salvation is for all who believe, whether Jew or Gentile,2 hence Jude refers to it as “the common salvation.”3
However, the context of Exo. 11 is the final plague that Yavheh would inflict upon Egypt. Yahveh would make a distinction between Israel and Egypt by personally protecting Israel while the destroyer4 passed through Egypt and killed all the Egyptian firstborn.
Acts 10:34 is referring to impartiality with respect to salvation, while Exo. 11:7 is referring to partiality or distinction with respect to a plague.
1 Acts 10:34
2 Acts 10:35 cf. Rom. 1:16
3 Jude 1:3: «τῆς κοινῆς σωτηρίας»
4 Exo. 12:23