And doesn't "some vendors they are" mean the opposite?
Yes, unless Yoda you are.
Really depends on how you say “some”
I will die on the hill that "SOME PIG" from Charlotte's Web was merely an existential determiner.
Even more common with "the". "They are THE vendors", which is either to say that those are definitely the vendors referred to elsewhere, or that they represent the archetype of vendors (whatever that is). Language is weird.
Exceptional rather than excellent I'd say, i.e. not necessarily positively exceptional.
Yeah, definitely inflection-based. A more relaxed one would indicate "a small amount", which for the opposite could be directly swapped with "many".