Follow the below steps:
1. Create 2 sets for each of the requirement in your problem
SET1 - Create Top N Customers
Right click on the cust - id and go to create and select set. I use N to provide through parameter.
SET 2 - Regular and irregular customers
Create 2 sets for indivisual year i.e current and previous year.
Now create a combined set to show common/regular customers or irregular customers by comparing years.
2. Create a combined set with SET1 and SET2.
Select both the sets and ten right click on the set and click on combined set.
Now choose Type of set i,e both inclusive or exclusive or shared member set.
3.Now use the combined set to show dynamic selection.
Hope it helps you!