The ScrollView component is a generic container that allows for scrolling, but it's not ideal for mapping over a large collection of list items. Instead, the FlatList and SectionList components are recommended for improving app performance when rendering long lists of items. The FlatList uses virtual scrolling to improve performance by only rendering items on screen, while the SectionList offers extra features related to list headers and footers. Manual track subscriptions can further improve app performance in large video calls by not subscribing to media tracks that are not currently being used. Developers building apps for large video calls are encouraged to use Daily's manual track subscription features. The onViewableItemsChanged prop of the FlatList component allows developers to know when to manually update track subscriptions.