which digital format for old Hi-8 home videos? I have a rather large number of old Hi-8 PAL videotapes, that I managed to convert to digital video using El Gato EyeTV Hybrid through an S-VHS cable.

That solution worked fine. It may not be the best quality, though I think that there isn't much quality to preserve beyond what I got. I don't know that, as I have no way to compare to other solutions. Comments welcome.

One fact about that solution is that it produces MPEG-2 video. The total disk space used for my videos is 168 GB.

I don't like MPEG-2 as a format: its compress rate is not great, it's difficult to process. What would be a better format for archival? Relevant features (in no order):


compress rate vs quality (saving disk space is low priority, preserving quality, poor though it is, is high priority)
long term support (avoid bit rot)
adequate for video editing (at least easy to import in common non-linear editing software. I am on Mac, so that would suggest Final Cut or maybe even iMovie).
interoperability/compatibility with Plex and typical DLNA servers/players.


Despite being a bit weak for point 3, I tend to favor H264. I converted all my videos to H264 using Handbrake, with its default H264 HighProfile preset. I saved a moderate amount of space, going down to 1.22 GB total. 

Is there any point to converting those videos to any other format (codec/container) for archiving?

Thanks
Difficult to reply without knowing if you aiming for a full lossless codec or a lossy one can go too. You talk of H264, but this codec can also be used in a lossless way.

If it was for me, and storage doesn't matter I would go for a true (pixel per pixel) lossless codec.

Here, excluding some other "good but insane storage hungry" lossless codecs your choice is between:


FFV1 codec, a pretty good choice for archival purposes.
H264 codec used in loseless fashion, that take less than the above, but is also handled not so well by NLE out of there.


In case instead you want to retain only a good video quality (let's say visually lossless but not pixel per pixel) you can go for an H264 with a crf let's say about 16 or 18.

Obviously is pure nonsense use lossless codecs if you already acquired media with a poor mpeg2. My suggestion is referred to the first video capture itself. So you should capture and save directly in FFV1 without any intermediate steps, then decide to transcode in lossless h264 or lossy h264 or just keep the FFV1 based on your storage needings.