I wouldn't get too excited about the adapters, the autofocus is really hit or miss, as is the lens performance
IF you have a look then some lenses seem to autofocus well but other really struggle, e.g. most of the 50mm lenses are useless
http://briansmith.com/sony-a7rii-canon-ef-smart-adapter-tests/
And then there is the general problem if wide angle lenses:
http://www.kenrockwell.com/tech/comparisons/2015-10-16-a7r2-5dsr/index.htm
You really want to be looking at native lenses if you are serious.
And if you really want to go small then you need a smaller sensor, the Sony FE lenses are the same size as canon, actually the 70-200mm f/5.0 is bigger and heavier which is not surprising because the Sony will need a longer barrel to make up the shorter flange distance.
Sony needs to hurry up and release some compelling lenses
