I ordered a Lancool 2 Mesh Performance case, and I would like to know if the stock case fans are good quality or should I replace them with Noctua case fans? Will I see better temperatures and/or noise levels with Noctua case fans?
You'll absolutely see lower sound pressure levels, depending on what fans you get. As far as better temperatures, that really depends on too many factors for a simple yes or no answer.
I'll pretty much guarantee though that the fans that come with that case aren't much different than any fans that come with any cases, including those from Corsair, Fractal design, NZXT, Phanteks, Cooler master, Thermalfake or anybody else. Generally speaking, in the majority of cases, no pun intended, any INCLUDED fans are going to be pretty cheap as the profit margins on cases are already pretty small and if they included any sort of decent quality fan they'd make no profit at all.
The first thing I usually do when I buy a case for a build is set the stock fans aside to either sell for cheap or use in something where noise levels are not a concern.
My advice however is almost always the same except for in a few cases where I know the included fans are particularly crappy, and that is, use them. It doesn't make much sense to not at least TRY them out, as is, to see if they work for you because it's always possible that the noise levels are not bothersome to you and that the performance is fine. Aside from a handful of very high end, overclocked systems, practically any case fans will work fine for performance so long as you have an adequate number of intake and exhaust fans, and that the right fans are oriented as intake and exhaust that should be for each given location. Try them, if they are annoying or inadequate, THEN replace them. Don't spend money needlessly. Be sure you really need to first unless you just have a bunch of money burning a hole and want the very best right from the start.