Currently, you can filter Special:RecentChanges/Watchlist by userExpLevel. However, for the API:RecentChanges module, you only have access to the the rcshow filter, which does not include, say, newcomer.
It would be good if any Special:RecentChanges/Watchlist URL could map to an equivalent API query.
Use case(s): Allowing API queries to produce the same (or at least similar) result sets to those available in the Special:RecentChanges/Watchlist pages. For example in "popups" gadgets when hovering over links to RC/WL pages.