The main difference between in-person and online therapy are the techniques used. Some (such as techniques used in the treatment of trauma) are not suitable for working online.
Indeed, conditions such as psychosis or people with suicidal thoughts are best treated in person.
With in-person therapy the therapist can ‘read’ your body language much more easily compared to looking at you on a screen.
With in-person sessions, you and the therapist will more easily be able to use the therapeutic relationship and the ‘energy’ between you. This can often point to relationship dynamics you have with other people outside of the therapy room. This is not so easy to identify when working online.
That being said, good therapeutic outcomes online can be expected if you’ve developed good rapport with the therapist, feel safe, and have created a space where you won’t be disturbed (by family members, pets etc.).
A competent hypnotherapist will still use hypnotic techniques online (though may avoid using certain techniques with certain people for safeguarding reasons).