sorry about the lack of info i wrote this all before i had to be at work... My laptop is a Sager NP8651 / Clevo P650SE, and nevermind their helpdesk gave me the answer: one is keyed for nvme and the other for sata, however both slots can use sata at same time.
the only question i have to ask them is if i use the m.2 sata drives can i still use the 2.5 drives too, for 4 drives at once.