The search using the Filter gramplet’s name field is complicated by it being a multiple parameter pattern search. It searches each word across a multitude of name-related fields in the database. Each additional word decreases the performance.
The searchbar was a more responsive option in older versions of Gramps. But I seem to recall that it was “upgraded” recently form a simple single‐string ‘exact’ search to the same ‘multiple string, multiple pass’ search in a recent update.
In past discussions, @SNoiraud has recommended using the RegEx option to force the Filter gramplet back to a single pass search. However, another thread on the forum says that RegEx performance took a hit under 6.0
There are other gramplets that use other name searching techniques with faster response. And Nick suggests experimenting with increasing the caching size. See the postings by @Nick-Hall and @kku in the following discussion: