You might try "FastStone Photo Resizer". It's freeware. It can batch process files. Resize to your specs ... I use it for email since I can only send ONE pic at a time at full res JPG thru many ISP's. I think someone on this forum mentioned it. I used to use other software but it wouldn't run on Windows 10.
I have used a number of different drives over the years and the only failures were with Seagate drives. I had a Seagate Free Agent stand alone that failed but it wasn't the drive but the enclosure electronics. I have also had 2 1TB Seagate drives fail that were in a RAID array. I switched to Western Digital and haven't had a failure. I did have a solid state drive fail a couple of years ago.
A true backup is a duplicate of the original files. In fact, you want a full system backup that will allow rebuilding the hard drive in case of a crash.
I don't understand the part about "M" sync. On the older cameras this was for flash bulbs. Electronic flash uses "X" sync. Then of course there are Focal Plane flash bulbs - but that's a different story.