We've had 6 rescue dogs between me and my mum over the years. All bar my current dog were UK rescues. They included a purebred Belgian shepherd breed (who ironically had the worst health of the lot of them; the rest were mixed breeds).
My current girl is from Crete. She had some issues due to under-socialisation as a pup, but she's honestly the best behaved dog we've ever had, 99.9% recall, devoted to me, quiet, amazing with cats, kids and other dogs - just the best.
But all rescues need time to settle. Look up the 3-3-3 rule.
All dogs, rescues or not, need you to invest time and effort into training. We paid for a behaviourists with our Crete girl, despite our experience, and it was 100% worth it.
And all dogs, rescues are not, are individuals; you need to give them time to see their personality come through, and mould yourself around those personalities as much as you expect them to mould around yours. Allow them to be dogs, to have fun, invest in positive reinforcement and all of that.
Older rescues are easier than puppies in many ways - all of ours were housetrained within a few days, for example. Didn't wake us up at night. Training was a breeze etc. Personally, having seen friends go through the puppy stage, I'd never do it!!
I've heard mixed reports of dogs from Romania, just because they are treated so incredibly cruelly over there. Many have trauma. Make sure the rescue offers full back-up and commits to taking the dog back if you have problems (not all rescues are equal, do your research and read through their social media posts - the ones that blame returnees are ones I'd avoid like the plague, for example).
Personally I'd never, ever buy a puppy or a purebred dog. Dogs are the most incredible things, a species that has adapted over millennia to live with us - they communicate across species (ie with us) in a way that's entirely unique - and so why we think it's OK to cast them aside like unwanted toys is beyond me. Rescuing one is one of the best things you can do IMHO.