@Hollie49
As to your first question, my message would depend on how the guest booked and if they have already provided me with any information or not, if they have answered the pre-booking questions or not, what information is on their profile etc. I tailor the messages.
Unless you are crazy busy with multiple listings, I don't think it's great to have a generic response, but you could have a pre-prepared response that you tweak for each guest.
Are you using instant book or can guests only request to book with you?