I recall “le” is just a preposition meaning something like “to” the noun it prefixes.
The two phrases are otherwise consonantly identical, with very slight vowel differences that I’m sure mean something grammatically but I’m not even remotely good at Hebrew. The NIV super-literal confirms that the Lamed consonant is a only a preposition, though (they translate as “into-living”): whatever the two words are for nephesh, they’re close grammatic cognates. The lamed is irrelevant for purposes of this inquiry I think. (Green’s superliteral ignores its presence altogether anyway.) I suspect the slight vowel differences amount to singular at Gen 2:7 and plural at Gen 1:20.
NIV translates the final clause of 2:7, “and-he-became the-man into-being living”, but I suspect “into-breath living” would work, too.
1:20, “let-them-teem the-waters creature breath-of living”
Green’s superliteral 2:7, “and became the man a soul living”
1:20, “let swam the waters (with)-a-swarmers having soul living”
Concordant Hebrew superliteral, 2:7, “and•he-is-becoming the•human to•soul living” LNPhSh CHIE
1:20, “they-shall-roam the-waters roamer-of soul living” NPhSh CHIE
I’ve provided the Westminster Leningrad Codex transliteration of the phrases in question with the Concordant Hebrew superliteral, as noted above: the two words are consonantly identical aside from the preposition Lamed.
In conclusion, the term at 2:7 does show up at 1:20. I don’t think the grammatic vowel distinctions are going to amount to any significant difference of meaning between the two verses.
(However, for God’s sake definitely keep pinging the Ancient Hebrew guy!–I know next to nothing on the topic of even modern Hebrew. )