Yes it's plenty for the system, as for as the certification the Bronze, Silver or Gold doesn't really matter, its the components inside that do and that unit is good quality.
It will handle the GPU overclock however if your actually getting a 1080 for that price in Canada I'd bet it's been used heavily to mine cryptocurrency.
Not really as I don't know much about those types of adapters but the one you picked may work fine, just make sure it's compatible with Windows 10 (check manufacturer website) and you should be fine.