Do understand that your target with this setup was to load test the Swarm manager and 30K is quite impressive.
Did you do / are you planning to do a test with other than the low end T2.micros to see how much of the API latency might be related to the type of nodes used.
In other words - if my intention would be to minimise the API latency - how would you approach this.
Planning to run a Swarm test (with a few 100 nodes) on Digital Ocean where we have 2 nics per machine - by this we can test latency / response time of the containers to their external work load plus to the API / Swarm manager on separate networks & nics.