Is this free Resolve or Resolve Studio? The latter supports more formats than the former.
Generally, all the DSLRs out there shoot H.264 files, which is not a great format for post. My general advice for DSLR workflows is:
1) organize all the files by shoot date and camera card number, so each file folder would be A1_03112019 [and so on]
2) add a unique prefix to the heads of every file to create easy-to-understand file names (like “A1_03112019_C0001,” “A1_03112019_C0002,” etc.)..
3) transcode all of these Long-GOP H.264/H.265 files to a high-quality codec like ProRes 422HQ or DNxHR, and keep the file names and folder structure exactly the same
4) archive the original files somewhere safe, just in case
5) do the entire edit with the transcoded files and consider them “the new masters”
6) now, when you do the conform in Resolve, every file will have a unique file name and even though the camera timecodes will still start at 00:00:00:00, there will be no conflicts because of the file names.
7) it helps greatly to have the editor create a reference file that has visible timecode and filenames for source files, as well as record timecode for the project itself.
Variable speed changes are a problem for all edit systems and cameras, because there is no simple provision for variable framerates in XML (plus different playback methods like frame-blending or optical flow produce different results). One way around this would be to just export the variable frame-rate clips and consider them a self-contained VFX shot. The alternative (which I have done) is just to manually varispeed the clip within Resolve and eyematch it to the reference video created by the editor.
This is a proven workflow that can work. I’m not a fan at all of productions using cheap cameras that have no internal jam-sync timecode, because inevitably there’s also other problems like exposure issues, sound problems, and other things that basically come with the territory. But I get that not everybody can use an Alexa or a Red camera, and sometimes you have to deal with what’s there.
There is more to it, but I I would point to the following books as fairly thorough references on the subject:
“Modern Post: Workflow & Techniques for Digital Filmmakers”
by Scott Arundale
https://www.amazon.com/Modern-Post-Workflows-Techniques-Filmmakers/dp/0415747023
“The Guide to Managing Postproduction for Film, TV, and Digital Distribution”
by Susan Spohr & Barbara Clark
https://www.amazon.com/Guide-Managing-Postproduction-Digital-Distribution/dp/1138482811