Linking multiple items from one board to single item on another board from a particular group

I have one board “Clients” and another board “Client Tasks.” In “Client Tasks” board, I have “Pending” Group, and “Complete” Group. I have mirrored the “Client Name” from “Clients” to the “Client Tasks” board. I have been able to get the tasks linked to that particular client to show up on my “Clients” board.

Is there a way to ONLY have tasks from the “Pending” GROUP in my “Client Tasks” board to show up in the mirrored column on my “Clients” board?

Also, is there a way to count the sum of these in another column? Tried looking everywhere for help and can’t find a thread laying this out, though I’m sure it’s been asked before.