This is how you change backup locations:
https://discourse.cubecoders.com/t/how-to-change-backup-locations/2783
And for Velocity/Forge you just create a Minecraft Java instance, select the Server Type you want, and configure things from there as you normally would.
https://discourse.cubecoders.com/t/setting-up-a-modded-java-minecraft-server/26535
https://discourse.cubecoders.com/t/minecraft-proxies-and-you/17673