When activating a child them I often have to reset custom menus. The menus themselves are still created but just have to be activated again. Is there a list of settings which are often unset when a child theme is activated? This isn't about theme settings, but core settings in WordPress
Switching theme does not purposely perform any forcible changes to configuration (that I can think of).
The changes that are typically observed are caused by mismatch in theme's features, for example menu locations and sidebars are likely differently named. So items assigned to them get treated as assigned to invalid location (which they are in current theme).