my memory may be a little fuzzy, but Hi8 should be backwards compatible with Video8 tapes. So you should be fine with either a video8 deck or a hi8 deck for playing back old content. (I ditched my Hi8 when miniDV became a thing.)
Yes, Hi8 is backward compatible on playback of Video8.
Oh, and Trask is right about capture hardware and software. No matter what you use, Standard Definition video played back on a HD or (god forbid) 4K monitor will make you cringe.
You can, of course, convert from interlaced to progressive frames and uprez to HD, but you are talking massive data size increase and then you are limited to either BluRay or File only playback. It's a real pain with no clear solution.
Easiest route is to keep it Standard Definition, interlaced and record it to a DVD, but then again, DVD players are getting long in the tooth...