upscaling videos on iMac 5k with VLC (or other player) - just enlarge the window? I have lots of old videos with low resolution. For example:

ID                                       : 1
Format                                   : MPEG-4 Visual
Format profile                           : Simple@L4a
Format settings, BVOP                    : No
Format settings, QPel                    : No
Format settings, GMC                     : No warppoints
Format settings, Matrix                  : Default (H.263)
Codec ID                                 : 20
Duration                                 : 1 min 46 s
Bit rate mode                            : Variable
Bit rate                                 : 2 743 kb/s
Nominal bit rate                         : 4 000 kb/s
Maximum bit rate                         : 3 000 kb/s
Width                                    : 640 pixels
Height                                   : 480 pixels
Display aspect ratio                     : 4:3
Frame rate mode                          : Variable
Frame rate                               : 28.508 FPS
Minimum frame rate                       : 2.097 FPS
Maximum frame rate                       : 40.816 FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Compression mode                         : Lossy
Bits/(Pixel*Frame)                       : 0.313


I play them with VLC. To upscale the video I just make the window bigger. Is there any better way?
Is there any macOS Sierra software providing better upscaling experience of legacy videos?
The fundamental problem is that your sources are low quality and going to a larger, higher resolution screen is just going to make them look more crummy than on a lower res, smaller screen unless you actually process the videos.
You can try interpolating the sources but it's a long process and probably not worth it. The best option is XMedia Recode. You can thank me later ;)