Happy to see the dashcam discourse.
Mine runs about 100mb/minute (these things don’t compress much), so make sure you consider that when buying an SD card.
You may not want to hold toooo much but I suppose you could oversize+underprovision to get some more write cycles.
Virtually all have a “save” button to avoid overwriting segments.
You’ll need some car mods if you want the to continuously record (and cutout if battery voltage gets too low). Mine at least has a tiny capacitor (or battery?) to detect movement and kick on for 15 seconds while disconnected for a few cycles.