I too have one Mormon ancestor who emigrated from West Wales (as did many people in mid-nineteenth century). some of his descendants are among my "closest" matches and so far I have linked
twenty-nine people with several more to document.
Once you start to cross-reference the matches, the number starts growing. This is because of ancestry's matching process whereby with your 5th to 8th cousins, only matches to 4th to 6th cousins are displayed.
Fr'instance: I have a 4th to 6th cousin
Tom who matches to another
cousin
Dick.
But when I look at
Dick's matches, he is shown as matching to
Tom but also to
Harry.
So, I can now connect
Tom to
Harry even though they are not shown as a match in Ancestry.
One word of caution: there is always a possibility of there not being a connection, especially in small rural communities where 2nd cousins can marry, sometimes without realising the connection.
A spreadsheet becomes a real necessity and it soon starts to get rather large!!!
p.s. I still can't find our common ancestor even though I know exactly where his family lived (very, very near my known direct line). This is where Gedmatch.com or Familytreedna.com become really useful provided you can persuade the other people to upload their results (for free by the way).