There isn't a simple answer to your question...
Firstly, the Note 9 does not appear to be listed as one of the devices compatible with Wifi-calling (see here). However, that does not mean that Fido won't add the functionality to Note 9 at a later date.
You should note that there have been discussions about customers not being able to use certain services (ie voLTE and/or Wifi-calling) with phones/devices not purchased from Fido because the IMEIs were not in Fido's inventory database. That said, someone was able to get Wifi-calling with their Note 8 purchased from Samsung Canada to work (see here).
Now, with regards to purchasing from Amazon.ca, you should be aware that many of the Note 9 versions available on that website (ie SM-N960F/DS, SM-N9600, etc) are not the Canadian version (SM-N960W) of the device (see here). It's rather unlikely that any versions other than the Canadian version will be provisioned for Wifi-calling.
In addition, you should note that other versions may or may not have the compatible bands/frequencies for the different networks. You can verify the compatible bands/frequencies here.
Hope this helps