There is great danger of overtightening plastic to metal, and female plastic fittings are prone to crack if overtightened.
My theory is that too tape makes the male too fat, and can cause problems. SO, two wraps of thin white tape, or one wrap of yellow tape. Brush on a thin coat of Great White dope.
The PPFA recommends this procedure : Hand tight, then 1/2 turn by wrench. If necessary to stop a drip, additional 1/2 turn.
Because plastic is soft, and the tape and/or dope is a lubricant, it is VERY easy to overtighten plastic to metal, distorting the plastic threads and causing a leak.
If you are a person who has hands like Mighty Joe Young, then just hand tight often is enough. For most of us, the 1/2 wrench turn will finish the job.
And as I have said before, if you are old enough to actually remember Mighty Joe Young, sit down and turn this job over to a youngster!!!