Using a reship service does not avoid customs. You still have to declare the value of the item and pay the respective duties to CBSA. The duty-free shipping limit from Canada to the US is $800 per transaction, and Mavic 4 Pro is certainly above...
What's the problem with DJI's intended app for the Mavic Pro... DJI GO4?
Since several years now you don't find it on the regular app stores... you need to get it directly from the DJI site & sideload it to your screen device.
Get it here for...