Do I need to reconfigure all the options when I do the upgrade, or is transparent the change?
If are there some changes in the config files between both versions , is better to copy the 2.8.19 config in a text file and paste after upgrade to 2.9
many menus have changed, lots of features have changed there names and locations. you probably will not be able to use the same config from the old version. if it is a router in real enviroment, i don’t recommend to upgrade. use 2.9 only for testing