My videos I work with are all SD 720x576 PAL from a 1998 Sony TRV-45E Video8 Camcorder (PAR/SAR 16:15, DAR 4:3).
For me personally I found that deinterlacing them in Hybrid and converting to Square pixel outside of TVAI (TVAI also has the option to convert to Square pixel built-in) works the best, before i head off to TVAI for upscaling/enhancing.
To Deinterlace using Hybrid read this.
To covert to square pixel with Hybrid, read this (only the portion that talks about square pixel, the rest is not relevant for you)
