Careful of your generalized assumptions your laws differ with ours, plus you don’t have first hand experiences with controlled delivery or even getting a cbsa letter or even dealing with border customs.
Again, please refrain advising people without any knowledge or evidence.
The legal standard for a search warrant is essentially identical in Canada and the US.
The idea that a targeted controlled delivery is foiled by refusing to sign for a package, that all the planning for what is inherently a high risk operation, the prosecutor's groundwork, the necessary surveillance, will all be dependent on whether you sign for a delivery is nonsense.
If there was sufficient evidence to acquire a warrant that's what they'd do,
Again, normal people take delivery of whatever arrives. Maybe I ordered something and forget. Maybe it's a gift. Maybe I won a prize. It's abnormal to leave it outside or refuse it.
Taking delivery of a package is never a "smoking gun" that can be used to prosecute, only a pretext to place you in possession of contraband so they can search for the necessary corroborating evidence or extract that evidence from your mouth if you're stupid.
In the absence of anything. else, the hearing would be something like:
"This package was delivered to your house."
"I have no idea where that came from I didn't order it."
"Guilty!"
Look folks, the best way to address concerns about what could happen isn't to let your imagination run wild. The internet is filled with news accounts, police statements, and court documents. Look it up yourself. Pay attention to how these things are done with say, a fentanyl bust using a controlled delivery. It's never just the delivery. A signature is never held up as evidence of guilt, in fact it's an unnecessary impediment when they can just hand it to you or watch you pick up the box and bring it inside. Finding one for PEDs will be far more difficult, but an even better lessen in how to protect yourself if you can.