Currently, I use a server and multiple best option the office. I have a laptop that I use as my main work computer. It has plenty of room that I could use to back up the Amazing Charts information. I also have a laptop at home that I use remotely. It has room for storage as well.
Utilizing any drive space that isn't on the server is fine, but it isn't optimal. In the situations you are describing, you would have to remember to make sure those computers were ready to accept a backup, e.g. connected, turned on, etc. The best media that is at the office would be external drives that are connected either via USB 3.0 (if possible) or SATA. (You would want multiple drives (two to five), each containing multiple backups.
