The strings are very important. If the strings aren't okay, the best Ukulele will sound wrong. Sometimes, this is the case with usually good strings. I had that wiht Koolau Golds for example. Every string but the C-string sounded nice and the intonation was correct, but the C-String seemed to be awful. The intonation was wrong after the 2nd fret, so I had to replace them with Aquilas (It sounded wrong to me, it sounded wrong to a blues guitarist who plays the guitar for 30 years and it sounded wrong to my chromatic tuner)
There can always be a flaw in good strings, but usually they are flawless. With bad strings, however, the intonation is usually wrong and if you have a correct intonation, you're lucky.
But an important thing is that you have to give the strings some time to settle after you put them on the Ukulele. Don't judge on the intonation just after you put them on. They have to stretch and for the first day or days they will be constantly out of tune and you have to retune them.
Furthermore, bad strings seem to be constructed wrongly. It feels strange to touch them, some are even sharp and cut your fingers, some are way to thick or the sound outcome is just bad as they are not able to project the vibrations on the top, as good as
quality strings.
So I never keep the strings coming on a new ukulele (besides I know that there are quality strings on it) and if the intonation of a string is just wrong even after 2 weeks of letting it "settle down", I change them. Moreover, I change strings often, firstly, because I want to try other kind of strings, new materials, new brands and secondly, because the strings show damage after some time of playing which is the case with metal wound low g strings.