Mixing questions on Base come down to flow shape. Count how many senders feed one address and how many receivers it pays next. The address format shows none of that.
Reading the shape
The native coin on Base is ETH. A single address that gets many small inbound transfers and sends them on in a short span deserves a closer look in the public explorer.
What the free check adds
It gives the transaction count and the OFAC screen as a starting signal. The pattern work happens by hand.