You can connect using SSH, and have full shell access, including file download and upload.
You can also enable a web interface on the device, and access it through the USB connection. Another way to manage data on the device.
Finally, you can use an excellent third-party tool, with a small one-time payment (or not, since this is open source): RCU, the reMarkable Connection Utility.
I'm using this one, nothing magnetic, it protects all sides and is thin and light. And surprisingly cheap. I love the rather unique design, especially how it shows off the tablet with its transparent back.
Two caveats: the pen holder is absolute garbage, just ignore it even exists. More of a small issue, the hole for the USB port is so thin it only works with the official reMarkable cable. Regular USB plugs are too thick.
https://www.amazon.co.uk/gp/product/B0B3J27K95/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&th=1