Never tried Biotin but my baby was overdue by a week and someone in my antenatal group suggested taking caster oil.
Never again!!!
Not to be recommended and it made no difference as I was still induced.
Hair grows in cycles (grow, rest, fall out) so there's not a huge amount supplements can really offer unless they can prolong the growing period before it gets to the resting state.
I think ensuring a healthy balanced diet is probably the most sensible plan and no smoking at all and only limited alcohol. I honestly think if people smoke then any benefits from diet or supplements is totally wasted.