The terms are honestly meaningless at this point, as each provider will have their own interpretation and comfort levels.
As BenDover said, you'd imagine that GFE would be like a girlfriend, but often times it is not. To be fair, some of my girlfriends were into greek, but others were not, attaching services to the terms doesn't always work out. That being said, not offering kissing and claiming GFE is a bridge too far, cause I've never had a girlfriend who didn't want to at least kiss.
In 2024, I think that the terms now are more geared towards the experience of the encounter.
For GFE, most of the time you'll receive a more warm and intimate service.
PSE would theoretically be more intense and wild.
Though, in my experience, PSE just costs more with no real difference, as your experience is often determined more by chemistry than anything.