What's the smallest machine Premiere Pro will run smoothly on?

small laptops are good if you need a display screen, but its not till around 14-15" screen size and at or over 4lbs that they have nvidia video cards included. the nvidia video cards are many times more powerful than the intel graphics and can help premiere fx and cineform media. i'm not sure if the intel graphics in the surface pro can accelerate cineform or not. you may have to see if premiere is using it for the mercury playback engine.

if you already have something like a tv or portable monitor for a display and you just need a computer, the Intel NUC Skull Canyon NUC6i7KYK kit may be a good option. its a barebones kit, so it would need memory and ssd, but should come in at around $1k and be very small and light. it also says it has one SDXC slot. the intel nuc doesn't have nvidia graphics, but it does have an upgraded intel graphics that should be helpful. its processor is the HQ series which are about 2x faster than the intel "U" series in ultrabooks or 2-in-1's like the surface pro.

Have you tried using Cineform (GoPro Studio) to make it easier for Premiere to handle?