The mouthiness is definitely normal, some are real full on with it...
I love a house line btw, I use dead lightweight ones - I’ve got a 5m one just now so I can tie it round my waist, he can still be effectively loose in the room (big rooms) but if I need it - it’s just there.
Mine isn’t too bad... because he’s older and he was in with the rest of his litter all that time, just a bit of toe and finger nibbling. One of the few things that’s not causing major issues, lol.
But if they’re on a houseline you can get them away from kids without having to use your hands and then distract them.
It’ll be worse when they’re excited and when they’re overtired... and yes it’s normal for them still to be doing it when they’re older, it doesn’t just suddenly stop, just slowly fades out, usually around about the time they’re teenagers.