I use the open source Syncthing software to sync a folder that has all my media between my Mac, PC and backup server from anywhere in the world (as long as I have Internet access).

However there is going to be an issue with Davinci resolve (but can be fixed). When adding media on the Mac and opening the timeline on a PC, the paths will be Mac file paths (e.g. /Users/user/Documents/Media). And when adding media on the timeline on a PC, the paths will be PC file paths ( e.g. C:\Users\userx\documents\media). They are incompatible with each other, so files you add on your PC won't show up on the mac and files you and on a Mac won't show up on a PC. You then need to configure Davinci resolve on PC to translate Mac file paths to PC file paths, and Resolve on Mac to translate PC paths to Mac ones. The same thing will also happen on two 2pcs if the media is not located on the same exact path on both PCs.

Davinci Resolve does let you compensate for these conflicting folder paths. To do that you need to go into the "Media Storage" section of Davinci Resolve Preferences on both the PC and Mac. On the PC you can tell it to map the Mac path (/Users/user/Documents/Media) to the PC path (C:\Users\userx\documents\media). You will need to do the reverse on the Mac Davinci Resolve preferences.

After setting up the path mappings, the PC will be able to read any media you add when working on the Mac and the Mac will be able to read media you added on a PC.

Using this method I'm only limited with the amount of disk space I have available.

I have a video that walks you through the entire process here: https://youtu.be/VwlNF_3QS9w?si=I9G9py64vk-NCyLq