PE is a funny sore spot for me. It’s almost impossible to obtain if you’re not working with other PEs, which is unfortunately the vast majority of engineering roles. I think we have one in my company and he’s in a different state. I have a master’s degree in EE and 15 years working as an RF engineer, but I’ll still see a handful of people saying we’re not real engineers because we’re not holding a PE license we’ll never need.

A professional engineer would be someone who's chartered with a recognised engineering institution (Engineers Europe and it's related Orgs in Europe, Engineering Council and related orgs in the UK, Engineers Australia in Australia etc) and the title would depend on the what the institution want to call them. The professional instution outlines ethical and behavioural requirements to maintain membership.

An Engineer usually refers to someone who does a job related to design and planning for a technical discipline (civil, mechanical, structural, electrical, software etc). The job role usually requires a degree in he engineering disciple, but if you were a particularly fantastic and experienced technical person you might be able to fill the role without one. There will likely be areas of knowledge where you'd be lacking in that case though.

I'm saying the job role could be made to require the chartership to help enforce adherence to the ethical requirements of those governing institutions.