Done right, the tape is foolproof.
You won't get any in passages like a brush on paste may do.
But all teflon tapes are not the same!
Some are very thin and substandard - and who knows what they are made of, just because they are white.
Get a name brand that states it will take heat and oil contact!
Teflon paste that is oil and heat rated is very good, but watch out for getting in in passages.