No, I do not believe smuggling does not happen, but once the UK gets it's 'great trade deal' from the US the incentive will increase significantly. To prevent that significant border checks are needed.
The other countries with a land border with the EU either do these checks in their (airports), like the scandinavians and the swiss or there are guarded border checks, like with the eastern/southern borders.
And as has been mentioned before, even with a backstop the UK could always take the same no-deal step they are taking now.
You are advocating the same having your cake and eating it too that the brexit camp keeps using. Either keep up with the standards that indeed you have no control over (like norway) and have an open border while a further deal is negotiated, or no deal and a closed border in which case the UK can import whatever non-regulated crap the US and China want to dump.
It's not the EU's fault that the mythical 'easy deal, we hold all the cards' failed to materialize and that a significant part of the UK still believes britannia rules the waves, rather than being the junior partner in this deal.
So your perception is that the UK will be full of cheap goods that the citizens of the EU are desperate to get their hands on, but EU rules won't let them. The people of Cork are gagging for chlorinated chicken, and that the pure white butter you get in the US rather than that horrible yellow stuff that Anchor markets is what the citizens of Dublin clammer for?
Why should smuggling be more of an issue into Ireland than it is now? Presumably the EU don't really care if Jameson's and Camembert are smuggled in to NI?
The Vatican is not in the EU but there are no restrictions between it and the EU. monaco is no in the EU and there are no borders restrictions between it and the EU.
Much of the argument seems to be this is not the way it is done this is not the norm. These are excuses not to do something. If you want something to happen you innovate you don't accept this is the way it was done in the past so this is the way it has to be done in the future.