My husband works for Kimberly Clark (they make Huggies, Kotex, Scott, etc.). They make the Kirkland Signature diapers and they are run on the same machines as the regular Huggies diapers. They are basically the same thing, only cheaper according to him. VERY little difference between those and Huggies Ultratrim. In fact, we only used Huggies until Kimberly Clark started making Kirkland's diapers. My husband is VERY loyal to KC, and feels fine supporting them through Kirkland Signature. We have been using them for about 2 years and have never had any issues. If your child does well with Huggies regular diapers (Supreme's are different- they are shaped different and meant to fit different than regular Huggies), then they will do fine with Kirkland Signature. Not all babies bodies do well with Huggies though.
As for the Kirkland wipes, they are not made by KC. I don't care for them myself, I like the Huggies better.