Where di you buy it? I’d say it is but a good place to start is : https://willmyphonework.net

I am buying it from OnePlus. 
I checked that website, but they don’t have the recent models on it. 

Assuming you are getting the North American version, it should work well with Koodo, since it covers all the bands on the network. 

Actually, both the Chinese version and the global version of the 8T should work fine with Koodo network

Regarding the 5G version of the OnePlus, as of now you can’t use 5G with Koodo network as they don’t have 5G yet. You can only use LTE/3G with Koodo.

Thanks! 
I don’t really understand phones… does one with 5G capabilities also have the capability to work on the LTE networks? 

Yeah, those 5G phones have all relevant LTE bands. 5G is just an extra.