Hi. I am also migrating to Debian 10, from other distro based on Debian. Probably I will do it this weekend, can't wait for Buster.
My tips:
1. Can't help here much, VLC works for me on everything I ever watch
2. Download various Live CD images and try them for yourself
before installing it on your laptop. Link to images:
https://cdimage.debian.org/debian-cd/cu ... bt-hybrid/Then you will know which one you like most and go ahead with that one.
3. Try Live CD images first, as mentioned above. If WiFi doesn't work or you have other problems on Live CD, they are easy solvable by googling/searching this particular driver problem. If, however, you have serious problems with display/audio/wifi or something, try this:
https://wiki.debian.org/Firmware, it reads:
A suggestion, especially when installing on unfamiliar hardware, is to download the firmware archive for your platform and unpack it into a directory named firmware in the root of a removable storage device (USB/CD drive). When the installer starts, it will automatically find the firmware files in the directory on the removable storage and, if needed, install the firmware for your hardware. You can find firmware downloads for your Debian version at
http://cdimage.debian.org/cdimage/unoff ... /firmware/.
So as you see, there is plenty of steps to take and mitigate problems, before you download full non-free image. Again, I recommend to download Live CD Non-Free image first, with your favourite DE flavour first

To make sure everything works. (link to them
http://cdimage.debian.org/cdimage/unoff ... bt-hybrid/)