Is it possible to change the color or font size in the RSVP block?
How does the RSVP work, will I be able to see first and last name of person responding and if they want to bring a guest can they add a name as well as their own?
You can make some changes to the RSVP block on the Design tab.
We provide reporting for your RSVP block on the Email Details page. You will be able to see total responses and well as individual responses. Read more about RSVP results here.
This block does not have a place to add a text response, but you do have the ability to change the text on the buttons which you could use to provide a "Yes, I'll be there with a guest" option.