Sming is fully "event based" vs the "loop based" concept from Arduino -> applications are written as callbacks.
As you have seen the conversion from libraries is not too complicated.
Sming has full and out-of-the-box support for http/tcp/ntp/telnet/mqtt IP connectivity, timers, pwm, gpio, json and much more. See more details on the readme of the github repository.
We are currently converting Sming to use the RTOS sdk from espressif.
With that the arduino compatibilty will futher improve.