>General Running>2 questions 2 weeks before tapering
You seem ready enough. Do what you feel like doing. I don't taper till the week of a race and I run 60-75 miles a week. If you think you will benefit psychologically from a 20 miler, do it, but I don't think you'd get any more benefit from it physically. Your miles were put in the bank months ago. I don't like pace groups. Run your own race. Might even want to forget the watch or do not look at it if your goal is to simply finish this race. I think you will do great and be very happy with your results!
Can you finish the marathon on race day without another 20 - yup. Will it hurt you - prob not. WIll is significantly help you do "better" on race day - prob not. Bottom line - a first marathon is exactly that - the first. You have prepared - finish your work as you see fit ... you will likely learn something about you & your running out there, after all those miles. Part of this sport is science but another part is the fun & learning & experimenting & realization that what may work for others - may or may not work for you. Hopefully this will be the first of many marathons for you!
I have done well in most of my marathons & been pleased with most of my accomplishments: sometimes I followed advice, other times I did my own thing - still learning & experimenting but I try to embrace the unknown. After so many races ... I am just learning to appreciate & savor the whole process with "race day" just being one of those other days I get out there and challenge myself.