Want to find out if they're an ENFP or INFP? Point an ENTP at them.
They both get along in similar ways but i find INFPs get frustrated at higher levels in smaller bursts, ENFPs have an underlying frustration but are mostly chill. INFPs will listen to ENTPs talk shit then join in when they can, although they can talk passionately. ENFP's and ENTPs will bounce off an interrupt and match each others bullshit.
ENTP + ENFP are usually described as "confusing", whereas ENTP and INFP i find tend to be more a relatively grounded person and their loud best friend.
These are obviously anecdotal and exaggerated but i hope it helps