I suggest adding the “Resize” setting at the bottom above the export settings, where the image size changes using ffmpeg before exporting. There should be an opportunity to set ANY size, including with a change in the aspect ratio and choose an algorithm (Fast Billinear, Lanczos3, Spline, etc…). Firstly, this will finally allow you to correct the aspect ratio, secondly, it will allow you to choose a compromise between quality and performance. For example, sometimes the best option is a 2x AI and then a cheap upscale. But sometimes the best is AI 6x and downscale to the desired resolution. Please, believe my experience (Google my nickname) this is a very necessary function.
Different models work with different quality at different ratios. For example, Proteus gives a great result in 2x, but not very good in 6x. Gaia HQ, on the contrary, gives the best result in 6x and so on. Now I have to use third-party programs like Premiere to compensate for the lack of this and some other TVAI functions. =(
Would you mind let me know how you get AI 6x ? 
AFAIK, TVAI only have AI model for 1x, 2x and 4x.
Just type 600%
Even more basic, when working with a mix of portrait and landscape orientation images, I would like to be able to set one resolution for whichever is the longer side, and have the program determine whether that is the horizontal or vertical dimension for each image. As it is now, I have to manually sort the portrait from the landscape orientation shots before running resize, which seems like a colossal waste of my time.
