My thoughts on this would be, use a macro lens that can capture each individual negative / slide into each image capture. That way if your camera sensor is 24 mp then the capture would be 24
mp. To get a quality image file will depend on the quality of the lens capturing the image.
I would recommend shooting in RAW, processing the files in your photo management software of choice, and then exporting them as JPEGs as needed. Your files will remain at their full size, especially if you non-destructively edit. Remember, JPEGs are a compressed format and you lose a lot of detail shooting your originals in JPEG.