It seems best to keep libraries updated if at all possible, so I checked into GIT, libaom version 3.8.0. It seems to have performance advantages worthwhile. Again as a reminder, default cmake version on Ubuntu 16 is too low to compile but can workaround as mentioned earlier (--enable-libaom=no on the configure line).

Will be verifying av1-svt work in the next few days as time permits.

One possible reason not to upgrade liabaom to 3.8 is that it gets you
even more work. The performance advantage over version 3.4 is there
(in my tests it is a good advantage, in Terje's there is not much
difference), but these become insignificant compared to using svt.
With this the advantage is huge. So one could neglect libaom and keep
only av1-svt.