First be sure to never update out of region.
Your chip should be able to block updates from disks.
If updates are allowed they happen before the game starts and you are prompted to accept the update- never update from an out of region game.
System Menu 4.2 currently breaks regionfree on chips, avoid 4.2 until new firmware is released for you chip- if you care.
Some games may load a black screen, this means that your wii is missing an ios needed by the game to run. These can be installed by allowing in-region updates from discs that contain the required ios- remember to avoid 4.2 as it may be out on newer games.
Your backup games will still work following an update from disk, so long as you don't update to 4.2 and the games are out of your region.
If you allow an update from an out of region disk you will semi-brick your wii.