How to setup syncthing on pi 4 with multiple computers?

Hi i just discovered this program recently and wanted to get some help on how to set it up.

Objective:

Create a private dropbox-like system that runs on my pi 4 and allow my computers to access it through my LAN and also outside remotely and able to Sync files across all the machines.

Computers i have: Pi 4 with docker installed and 2 ext 2.5 hdd’s Desktop windows machine apple macbook pro laptop A windows based laptop.

I have installed the docker image using this guide https://github.com/syncthing/syncthing/blob/master/README-Docker.md But now confused as to how to run this through docker and specifically want to know what this -v tag is on the readme?

Is the -v tag used to specify where i want the data folder to be in?

What happens if once i start syncthing via docker and i close the docker container, do i lose all my sync data?

How can i specify that syncthing uses my ext hdd (for example its location is /media/ext/hdd1) to store the synced folder data?

Can Synthing do the below:

Pi 4 having 3 folders on the ext drive called pictures, documents and music,

Have all my other computers sync to those 3 folders.

If my apple machine adds document 1 and 2 on the document folder, does that get synced across all my other devices either through my LAN or remotely?

What if i later migrate the container of synthing into a ubuntu server of my choosing and copy the sync folders i had before on it, and run the container again, can i maintain the same sycn data (assuming i tweak the synch connection of the other machines to now link up to the new server machine?)

Thanks in advance and looking forward to using this

These sound most of these are docker questions rather than syncthing questions.

If you are not familiar with docker and how it works, I suspect it’s easier and more predictable for you to run without docker.

Syncthing tries to use lan when possible, but will sync over the internet if it’s not possible.

It’s best try not to migrate syncthing, but just set it up from scratch, as people usually make mistakes and lose data.

For anybody else reading this thread, I would extend that good recommendation by suggesting to set up the new device from scratch, sync it with the existing cluster, and then remove the old device. The entire cluster does not need to be scrapped and started again.