The problem with the smaller file you have is that it's a sped up NTSC to PAL conversion. You can tell by the higher-pitch audio. Fixing it is a bit tedious.
As for the larger video, you can deinterlace and gently denoise it in most encoding software. Here's an x265 example made from that file:
The Disney+ set is fairly good in my opinion. No interlacing, full subtitles, but only 480p. 576p files are often stretched from their native resolution, so there's some philosophical debate to be had about which is better. If you want the absolute best version but still save space, I would say download the Russian 576p, re-encode it, then download the Disney+ version and extract the subtitles from that.