You're about to go down a big big rabbit hole ... and it's not helped that it's a fading technology, so modern stuff is leaving it behind in terms of options. It's been a while since I did any of it, although I kept the hardware for some of it. To me there are 2 aspects of it : capturing, then secondly editing.
Cut to the chase for editing ... to me, for basic editing needs and if you have all the footage on an external drive / nas. I think you'd be hard pushed to beat the value of a base Mac mini m4 (£600) + the creator studio subscription at £13/month ( includes Final Cut Pro and compressor, plus a lot more ).
That said, any modern PC (windows or Mac). will be able to edit at the hardware level... as you mentioned above, it then comes down to software. So many options. Best cheapest option: Davinci Resolve (free version). But beyond that, software cost can ramp up rapidly ... which quickly makes the Apple creator studio seem like good value on the face of it ( imho - although I've yet to try it as I've bought full Davinci resolve prior to it coming out ).
Capture:
Basic USB capture devices - Cheap and can work just fine, but I've heard of instances were audio can lose sync with video.
You could also buy a cheap AV to HDMI converter, then an HDMI to PC recorder device. Not tried myself, but may work well enough for your needs.
PCIe capture cards. I'd say that in terms of availability, Avermedia do some pcie cards C725B and CE310 ( I have one of these ... supposedly its slightly better ) . Windows only, but I liked that you can set the record format and record time in advance. So if you know you have a 65minute tape, you can set that, start the record on the PC, press play on the source and walk away knowing it'll automatically stop. I found it very reliable. Beyond that you're getting into rare and expensive cards.
An aspect I haven't explored fully, but would think about again considering I have a Mac now is some of the Blackmagic products which are conversion boxes / recorders. More expensive, but verging on pro production level items.
For the DV sources ... firewire is the easiest option. DV is essentially just the firewire protocol so if you can get a firewire device then it would plug straight in and transfer the raw data file as from the camera ( relatively large files, but easily managed). On a PC, you would likely need a PCIe firewire card ... usb adapters are mostly not going to work (general USB cannot normally transport firewire data unless its specifically a thunderbolt port, which are rare on windows PCs ). On Macs you can get firewire dongles which will plug into Thunderbolt ports.
No matter what you do, it'll only ever be as good as your source. And sVideo connector is generally considered better quality than the yellow/red/white RCA connectors.
Lastly, on that point of source ... one of the biggest improvements you can make to the source footage of VHS and similar is to run it through a device which has a time base corrector in it. TBC reads a frame of video and aligns the the scanlines of the interlaced footage and then sends it out for display. This means that it gets rid of the left hand side wavy-ness / flutter of footage and makes the picture much more stable looking. It really does make a big difference to tape footage. You'll need to do your own research on finding devices, but many of the older VHS / DVD / HDD recorder all in one devices have this feature ( they needed it to be able to save to DVD or HDD from VHS internally) . For me, I have a Panasonic one. I can play VHS tapes and then capture the s-video out. I can also plug in AV sources into the Panasonic such as camcorders, which then go through the TBC to get cleaned up, and then record the S-video out of the Panasonic. Heck you might even get lucky and find one with an HDMI output ... which would be simple to capture into any pc.
Like I said .... rabbit hole.
