Ghost has been a superb platform for my dev blog, and I'm hoping to migrate my personal blog over to it at some point in the future (it's currently using Gridsome).
As for forms, I think if you wanted a completely custom form, then you would have to use something like TypeForm or JotForm and embed that into your Ghost blog.
It tries to focus solely on publishing and blogging, but recommends other services you can tie in if you need to which you can find here - https://ghost.org/integrations/