Regen is primarly there on ebike NOT to recupture energy, it is there to greatly reduce grinding on pads and rim
which is so important on heavy ebike.
On my Tidal Force regen is designed beautfully smooth and strong and front pads last for years and years, longer than on all my regular bikes.
But don't expect so on E+ where regen is weak, jerking and simply badly software implemented.
Simply you need to ride TF to know the difference.