I will design a creative fillable letterhead template

Absolutely yes, you can type inside your word template, print and sign manually

No, You can not edit the address or logo, You can only type in it. However, if you want one that you can edit the address, order the extra gig.

Once you open the PDF, you type into the fillable sections. And at the bottom, you will see a signature field where you can digitally draw your signature. Once you save the PDF, all what you typed becomes un-editable and no one can edit it.

Kindly see the extra gig.