Can I substitute low fat greek yogurt for light sour cream in a high speed blender?
You can substitute one to one.

Many brands of "light sour cream" (Which is an oxymoron. Cream without the cream?) have a lot of gums and starches to stabilize the liquid as the fat would have done.

Brands that don't have gums dilute the fat with skim milk and are basically just yogurt anyway.

Regular yogurt is fragile. It is a delicate mesh of proteins filled with water. When it is blended the water washes out. However, greek yogurt has already had this done! So there is less water and it stays creamy and loses relatively little extra liquid even when blended.