Wonderment, building on and supplementing SBF's comment on shālach at Ex. 8:1, notes how a minority of translators render that verb as "send" while the majority prefer "let go."
The fact is that the word shālach can have both English meanings. While those two connotations may look different in English, that is not the case in Hebrew. In order for English speakers to see the semantic domain (range of meaning) of the word in Heb., consider "send" in the sense of "send away, dismiss." Once one does that, the at-first-glance difference in English between the two options "send" and "let go" melts away. If Moses is to tell Pharaoh "send my people away" or "dismiss my people," then isn't that the same thing as "let my people go"?
The overall meanings of shālach in the Theological Wordbook of the OT are given as "send, send away, let go" (2.927). That it can mean "expel" is clear from Gen. 3:23, Adam and Eve expelled from Eden, and from Deut. 22:19, 29, a man divorcing or sending away his wife. Isn't Pharaoh supposed to "expel" the Israelites from his domain?
It is noteworthy that the English translator of the LXX in the NETS version did not simply use "send" (which would be a translation of pempō) at Ex. 8:1, but "send ... away," from exapostellō. The literally meaning of it is "send forth, send away, dismiss." It is found in the Gen. 3 and Deut. 22 passages above for the Heb. shālach. Also on point is Jerome's translation of shālach at Ex. 8:1 in the Vulgate: dimitte, from demittō, from which comes our English "dismiss."
I hope this clears things up. It really is a false dichotomy to pit "send" against "let go" in Exodus 8:1 because translators there do not simply render shālach as "send" but as "send ... away," what the NWT reads, as do Robert Young and George Ricker Berry in his Hebrew interlinear (1897). A check of Fox and Alter (unavailable to me) here might well turn up the same.