I just ate a ripe shishito yesterday. I'd say they are Frank's red hot level of hot, with good flavor overall.These are all 2-3 inches if not a little longer now. I’ll let them be for now. I’d rather have cubanelles than shishito. Hopefully they get longer.
And your friend doesn't know what a Serrano looks like at all lol. They aren't wrinkly. Serrano are more like a jalapeno but not as wide. Definitely don't have any kind of wrinkling.
This was a cubanelle from last year.