https://www.teamrankings.com/nfl/stat/passing-play-pct
https://www.teamrankings.com/nfl/sta...first-down-pct
I tried to check their work and could find some similar overall stats on ESPN and a couple other data aggregators but couldn't find anything on the 1st down run/pass rates to corroborate their data.
It seems fairly trustworthy given I could verify that their overall numbers were accurate (everyone judges run/pass just a little differently due to RPOs and QB scrambles).