Congratulations and I hope it works out well for you.
It has worked out fairly well for us despite us being pretty naive and doing it all wrong. Our boy isn't the easiest dog anyone ever had but he's not the worst either and I don't think we've had hugely more issues than we might have done with a U.K. dog. I certainly know worse behaved pedigree dogs.
We didn't intend to import a dog. We actually tried to get a U.K. rescue dog but wound up with a Romanian one who had been brought over by a U.K. charity and was in a U.K. foster home. None of our local charities actually had any 'home grown' rescue dogs available to adopt at all. This was despite us having a secure garden, someone at home, no other pets and older kids and being open to pretty much any dog. We weren't getting turned down just told there were no dogs available. A lot of people seemed to be selling their lockdown pups on Gumtree rather than rehoming them via charity at that point.
We weren't really very alive to the importance of where he'd originally come from or the breed.
We were just told he was 'large mixed breed' and he is gorgeous and floofy and we fell in love with him but, as far as anyone can tell, he is likely a Mioritic shepherd which is indeed a flock guardian breed. He does alert bark loudly at the postie and delivery people and he is rather 'independently minded' aka stubborn. He isn't a calm bombproof pub dog. However he is friendly to people we invite into our house and to other dogs and people we meet in the street and he will obey a lot of commands if he is in the mood or if you have sausage. One big plus is he came fully toilet trained and has never ever had an accident in the house. He also has no separation anxiety, has always slept through the night on his own downstairs and is unbothered about being left for a few hours especially if he gets access to the sofa. His only major issue now really is that he is insanely reactive to motor bikes which we are finding hard to make much headway with.
Admittedly he is not as soft and trainable as a lab or a golden retriever but I don't think he is any more unsuitable as a family pet than a German shepherd which lots of people have. There's people on my suburban housing estate with pointers, Vislas, Weimaranas and Dobermans who are a lot more reactive and badly behaved than my terrifying livestock guardian breed.
He was tested for Brucella and vaccinated against rabies as well as all the usual vaccinations before he came to the U.K. and he has a passport with all that info on so I don't accept that he posed a threat to health. We didn't have any issue getting him insurance or getting a vet to register him. The rescue provide behaviour support and would take him back if we asked them to. We signed a contract not to breed from him and to get him neutered and we have done.
All that is to say that it is certainly possible to own a foreign rescue dog responsibly and I will still always maintain that it was the right thing for us to rescue a dog regardless of where he came from rather than to have bought a puppy regardless of how responsible the breeder was. Any dog can have a health or behavioural issue and any dog takes time, money and patience so why not expend that on a dog that already exists rather than encourage more to be bred.