Hi, I'm making my first documentary utilizing Adobe Premiere Pro CC 2017. My footage is from various sources, both my own filming and also archival from others. Since most of this is from 2010-2011, it was mostly SD (720X576). Accordingly, my sequence preset and settings were DV PAL, 25 frames/second, 720X576 and an aspect ratio of 4:3. During editing, under Effect Controls, I changed the Video Effects of the Motion(Position and Scale) to get all the clips to fill out the frame. However, in some instances when doing so, I lost part of the image outside the frame since these were clips from archival footage shot at HD 1920X1080 and so they were at 16:9, and had to zoom them up to eliminate the horizontal black lines at the top and bottom. Now here is my question:

Someone advised me that in order to have a better chance at being accepted at film festivals (which is my goal), I should unify all my footage by making a new sequence with a preset of HD (1920X1080) and placing all the clips in there and doing a "scale to frame size" and working on that sequence. Someone else told me that I should not convert from SD to HD, as this might actually hurt the quality/resolution of what I have, and Premiere Pro itself seems to indicate that it is best to make the sequence preset and settings similar to what is in the footage. A third person told me to keep it in SD but change the sequence preset/settings such that the aspect ratio becomes 16:9 and this will not damage quality (i.e. SD to SD) and will get the missing parts of the image in it, but will have a lower chance at film festivals acceptance because it is not HD. What should I do??!! (Also, if I am to go with the HD preset, should I go with interlaced 1080i or progressive 1080p?)