If you are looking for absolutely most powerful device but in smaller form factor than NUC then check out PC Engines APU.1D, this amazing board is x86 so it blows all other non-x86 devices away... it should be similar or more powerful that Mikrotik CCR Cloud Routers.

Software wise it can run FreeBSD, OpenWrt or Mikrotik OS.

[1] http://www.pluscom.pl/en/pc-engines-apu-1d-3xgigabit-lan-2gb-ram-t40e-cpu-board-p2412.html

- http://www.pcengines.ch/apu1d.htm

[2] https://schemen.me/routeros-on-apu/

- https://wiki.openwrt.org/toh/pcengines/apu

- https://forum.openwrt.org/viewtopic.php?pid=316913