These are photos of two leaves on my Peppadew. The Pimienta de Padron looks the same. I looked at the leaves under a magnifying glass, and these bumps do not appear to be on the surface. They don't wipe off. Some sort of blistering, or scalding? Worse??
Agreed with Jamie, Edema. It happens when the plant's roots take up more water than the leaves can use or dissipate. It's not usually a problem for the plant. Getting a fan on them helps.
Not necessarily. It can happen from high humidity, or warm root zone and cool ambient air.
I would say that if your plants aren't showing other signs of overwatering (such as yellowing leaves) then you don't have to worry about it being overwatering.