Does the game meet the criteria if theres never more than 64x64 pixels on screen? We want to use a smooth panning camera, which would mean pixels would get cut off at the sides. That would technically mean that a majority of the time there'd be more than 64x64 pixels visible, but the extra pixels would be cut in half, so the total surface would be the same.

So basically, can we use a normal camera, or do we need to use a filter that pixelates the game, even if we only use pixelart?

Technically a pixel is the smallest unit that a monitor can display. Granted with high dpi monitors, the term pixel has been a bit overloaded but for this jam, that means there can only be 64x64 units of color.

Any trick used to bypass this restriction will probably just look bad and likely negatively affect the authenticity rating.

I’d set your viewport to 64x64, scale it up in whole number multiples to make it easier to see, and accept the restriction.