Trail grading over there is a lottery at best. They’ve tweaked things a bit in recent years, most noticeably in chatel where grading was laughably optimistic.
As for Les Gets, the main red line on the Chavannes side is nothing like a trail centre red. It’s not that steep but it’s fast as hell with some enormous table tops (rollable) big gaps (chicken runs) and it’s unbelievably rough, particularly the section after the cattle grid halfway down.
The Nauchets side is maybe a bit closer but if it rains in the slightest it’s horrific.
Either way, it’s a big step up from a Scottish trail centre red.
You are right about Chatel – proper DH stuff over there (although there are chicken lines for everything).
The main Les G red though other than being a bit steeper and yes nasty braking bumps in places is a hoot. My 8 year olds loved it (tabletops not gaps) so generally it’s fine for most adults who ride trail centres.
Obviously… you’ll know what you like. The tour routes are good but don’t bother too much with the XC routes – very dull.