Hi,
You can use the same Ad customizer feed in different AdGroups. If you would like to use the
adGroupTargeting attribute of a FeedItem to restrict the feed item to only a specific ad group, you can specify a single ad group only. Please see this
guide for more details on using an Ad customizer feed in an Ad. The
AddAdCustomizer Java example shows how to create FeedItems with the adGroupTargeting attribute set to different ad group Ids and then create expanded text ads that use ad customizers for the specified ad group Ids. When these Ads serve, they will show different values, since they match different feed items. Example code in other languages is available
here.
Regards,
Shwetha, AdWords API Team.