I've been wearing Teva's for over 15 years. I wear Teva sandals for 8-9 months out of the year.
I normally wear a size 8- 8.5 shoe. I do not have wide feet & I do not have narrow feet. I consider my left foot is approximately 3.5 inches at it's widest. I like my sandals to be a tiny bit lose & my toes to be as free as possible of restrictions.
My previous  Tevas were  Zirra size 8. Teva  Verra 8.5  & Teva Terra Fi 3  size 8. SO, never did I think that this Teva version would be so different in size !
I've tried an 8, all the way up to 9.5 and they really don't seem to get longer & certainly not significantly wider. A 9.5 seems to be just right in length for me, but there is something off with the width & it rubs my left toe painfully. I gave up & went to my local REI store &  tried a Mens' M 8 Terra Fi4 and miraculously it was perfect. I would have bought it on amazon but they don't sell that small of a men's size. I really wanted a more feminine color but am ending up with the men's, even though it has a wider foot & ankle strap, it's just more comfortable.