This question relates to two verses which put Moses in a chain relationship which goes : God → Moses → Aaron → listener. It is unusual in the Bible because normally there is only one agent between God and the listener, such as God → angel → Moses, or God → prophet → people.
Exodus 4:16 – Moses “as God” to Aaron
“And he [Aaron] shall speak for you [Moses] to the people, and he will be as your mouth, while you will be to him as God” (Exodus 4:16).
Exodus 7:1 Moses “as God” to Pharaoh
“Behold, I have made you [Moses] God to Pharaoh, and Aaron your brother shall be your prophet” (Exodus 7:1).
The King James Version reads God as saying to Moses “I have made thee a god to Pharaoh” (KJV), as if Moses was to be a minor god, equivalent to an Egyptian idol.
Modern scholarly versions read the verse as God telling Moses, “I have made you like/as God to Pharaoh” (ESV, NIV, NRSV etc.). This follows the sense of the Hebrew verb for ‘made’ here, in appointing Moses to a role to Pharaoh (as to Aaron earlier), rather than actually making Moses become a deity in his own right. It’s a metaphor that illustrates the unusual God → Moses → Aaron → listener chain caused by Moses’ timidity. It’s a very different sentence than God saying “I have established you Moses as God” (sic).
Although there is nothing inspired about the Septuagint, it’s worth noting that the translators rendered Exodus 7:1 as “I [God] have given you [Moses] as God to Pharaoh.” The Greek does not use prepositions as in English “…. as…. to…..” but uses grammatical case to indicate “I [nominative] give you [direct accusative] God [indirect accusative] Pharaoh [dative]”. Which is the same thing as the English ESV, NIV, NRSV, etc.
Conclusion
As can be seen from the above the difference between the KJV “a god” and ESV, NIV, NRSV “as God” is not enormous, but the KJV is incorrect. If the KJV was partially corrected to render “as a god” there is still a major problem, in that the whole purpose of the God → Moses → Aaron → listener was that ultimately the real Living God was the one speaking. Moses was not functioning as one of Pharaoh’s clay idols, nor as a golden calf to Aaron, Moses was (briefly) speaking as YHWH of Hosts, the One God.