Sorry I’m a bit late responding but I have found that plastic store bought regulators are very inaccurate. If you are going to regulate the flow I would suggest buying a lead free, low PSI, brass pressure regulator from a plumbing supplier, or if you can online.
Personally, I adapted two 1/4” John guest ball valves to a 1/4 turn hose bib. I turned the hose bib almost all the way off to reduce the pressure, and then the second JG valve is turned to achieve my desired drip GPH and the third JG valve is on full.
If I ever want to test the accuracy of the drip I can just shut the third valve off, pop out the 1/4” tubing going to my sump, and put it into a bucket to test.
This is all run after a sediment filter and two carbon block filters which I would highly recommend if you are worried about chlorine and/or chloramines.