Both kits have the same Frequency and CAS Timings (9-9-9-24-2N), but have totally different IC's. Therefore, my best advice to you is not to mix-match any RAM.
ANS1: '2N' is the Command Rate (CR or CMD) is the Delay between chip select and command, or the number of clock cycles needed to send data.
ANS2: As stated above the Frequency, CAS Timings and Voltage of both kits are the 'same' at least on the surface. The problem is RAM has much deeper Timings which is influenced by the RAM's IC's, Ranking, etc. So it's best never to mix-match RAM. Further, I really don't recommend mixing Densities and especially not exceeding your CPU's Rated Memory frequency in those cases. It a matter of Errors and system stability.
Ideally, if you need >4GB of RAM then simply purchase a new 2x4GB or 4x4GB matched set. RAM is sooo inexpensive now that saving $30~$50 vs Stability simply isn't worth the headaches.