I recommend reading this: An Extensive Guide to Web Form Usability

1) I would highly advise not to have one large form. It's very intimidating for users to see a long form and would most likely discourage users from filling it out. As Revolt suggested, you should separate your forms into multiple steps (with a progress meter) so that it softens the blow.

2) This is more of a personal choice than a UX question. If anything, you should design it with a similar aesthetics of your brand and how you want your brand to be viewed.

On the side not, I don't recommend having the form automatically going to the next set of questions once the user is finished. Most of the time, I go through the forms I fill out before submitting it. This is also an unexpected behavior which the article advises against.

Sudden changes in behavior or appearance will make users edgy. Likewise, never introduce sudden changes between forms or between steps in a form.

I recommend reading this: An Extensive Guide to Web Form Usability

1) I would highly advise not to have one large form. It's very intimidating for users to see a long form and would most likely discourage users from filling it out. As Revolt suggested, you should separate your forms into multiple steps (with a progress meter) so that it softens the blow.

2) This is more of a personal choice than a UX question. If anything, you should design it with a similar aesthetics of your brand and how you want your brand to be viewed.

On the side note, I don't recommend having the form automatically going to the next set of questions once the user is finished. Most of the time, I go re-check the entries I filled out before submitting it. This is also an unexpected behavior which the article advises against.

Sudden changes in behavior or appearance will make users edgy. Likewise, never introduce sudden changes between forms or between steps in a form.