Mega rabbit hole to go down.
They’ll look like they’ve been upscaled no matter what way you try it … which personally sometimes detracts from the original look of the files. They are from the time, of the time, and depict the time. To me that’s part of the charm of some of the older videos.
Now what you could do, and I have done quite successfully in the past, is colour grade them and maybe a little sharpening. Old VHS and 8mm tends to have low contrast and tinted colours compared to what we are used to today. Even the free davinci resolve will be able to do a very good job of improving the contrast, saturation and tints of footage so that they look much better.
Lastly, what file format / video codec are they saved in ? Once graded, you’d be rendering the file out to a new file. There is little to no point taking a PAL video file wwhich is around 720x576 ( or whatever it is ) and rendering it out to 4K … it’ll look no better, and make for a huge file … keep it near the same resolution.
I’ve also read argument that favours the older MPEG2 format for older interlaced VHS / DVD footage compared to the newer h.264/265 AV1 type formats. MPEG2 having been designed for that era of footage makes it a good fit to save video using it. Not something I have explored very much to be honest … I don’t really recall there being a noticeable difference though either way In reality.
Whilst there is a lot of evangelical techie snootie-ness spouted around video and colour, at the end of the day, whether your footage looks good or not is subjectively down to you. For that reason, I’d recommend just having a bash at messing about and trying things. Make a copy of one of the files and try the options …
Try grading it. Resolve is free to try and includes the grading tools which are film industry quality.
export at original resolution in different codecs and bit rates.
export at different resolutions and see if it makes a difference to how it looks.
Lastly - if you want a starter setting for 10 … try adding bit more contrast, lowering the colour temp a little ( turns the whites from yellows to colder blue white ) and exporting at 480p using h.264 with a bit rate of 2Mbps and see how that looks.
