The W sizes also have a different waist position, i.e. higher waist. I am somewhat larger than you and am wearing 18W/20W, but will shortly be in the next sizes down; I started out in 3X (24/26). They are also proportioned for a larger bust (i.e. C-D cup instead of B).
Also, for me, an elastic waistband is still essential and the non-W size clothes have far fewer of those. They are also not proportioned for wider hips.
Actually, I prefer to make my own clothes because then I can get them to fit my shape properly. And the clothes I make are not generally styles found in the stores -- somewhat unconventional.
I recently got rid of most of my larger clothes and made/bought a whole bunch of new ones in smaller sizes. It was great. It happened to be at the time of year when they sell colors I can wear. Winter colors look horrible on me. And I prefer lighter-weight clothing as well.
Then I hit a stall and actually went up a couple pounds. That was scarey. I knew that I couldn't gain much of the weight I have lost because I wouldn't have anything to wear.
But now I'm glad I did it. I broke my stall, and not having any clothes to wear if I gained weight kept me on the straight and narrow.
So go out and buy those clothes! It will be a great feeling/experience and ultimately you will feel so wonderful and thin. And throw out all your fat clothes. You will never need them again. And after you do, post a picture of you in your new wardrobe.
;-Deb