I think it somewhat comes down to the kit source as to the quality of the original chain. ZTMoto engine kits come with a decent quality 415h chain that I have always had good luck with.
Most cheaper kits come with unsurprisingly cheap chain.
In either case, a lot of them tend to come very dry so I usually give them a warm gear oil bath.
There is a store on Amazon called the Jeremywell Store that sells bulk length of Unibear branded standard chain. Unibear is a Chinese brand, but they are actually decent quality chains that are also quite popular in the Chinese dual sport community. I replace my kit chains with this particular brand.
He sells
10ft/240 Link and
50ft/1200 Link options. Or, roughly enough for 2 bikes or 10 bikes respectively.