Both as they are in the 4SWW
Both at full chakra
Location: Where Gaara fought Kimimaro-Large field surrounded by trees
A bit odd but their fighting styles make initial assumptions questionable. Choji is on a timer since Gaara can immediately start creating more sand until he can drown Choji (No matter his size) but from the get-go, does Gaara have enough sand (in his gourd) to subdue Choji? Gaaras fight with the Reanimated kage normally should give him a strong argument but this battle was fought in a desert, on his own turf. I just see Choji super sizing and Gaara's sand struggling to suppress him(Similar to how Gaara couldn't hold Madaras Susanoo).