^Yeah the L is useless but I think there's quite a bit of misinformation about it.
L-meth does cross the BBB just like d-meth and binds to the same receptors IIRC, it just has a weaker affinity. L-meth has pretty much no effects on dopamine nor serotonin, relatively speaking, so it doesn't get you high.
As for noradrenaline, which is thought to be the cause of the unpleasant side effects, D-meth still realeases MORE NE (overall) than L-meth and regular d-AMP releases even more than both of those.
Pretty much everyone reports having much more side effects from racemic meth and I believe it (never had racemic myself) but it might be because they took more than they should have, which is understandable since you'd have to double the dose to have the same amount of d-meth (if you're used dextrometh).
There's a nice table with various binding affinity values on reddit if you're curious. I could be wrong since there isn't much info about those values online, so if someone has access to a newer scientific paper saying something very different then feel free to correct me.