I am reasonably sure you will need a separate router between the RB2011 and each test device to provide NAT for each test device. Something like this post
And you won’t need a separate vlan for the connection from the RB2011 to the NAT routers, since the NAT routers will each have a unique address on the RB2011 side.
If you don’t need high performance, you could probably get by with hap lite (and turn off radio), just use two ports, and it will probably be limited to v6 due to limited memory in the hap lite.
If you need more performance or the ability to use v7, you could use hex, hap ac 2, or hap ax lite (but still one per test device)
See this thread Problematic destination NAT