Lapras ?

Here both Lapras and Snorlax are so rare that I power them all up despite of IV and moves, I always walk with the one which needs the least amount of candy for the next power-up

I don't think that your second Lapras with low IV worths powering up. As she has a defensive moveset you can power her up to certain CP based on the gym s where you live.
About snorlax, both of them have worthy IV's. Start powering up the one with better moveset and when you have resources you can care the other one if you want.

Prioritize your 2196cp Snorlax first then you look to this 49% Lapras. The moveset is not that good (but not that bad too, A for attack and B for defense), but he will still with a river of HP and a defensive beast besides he have a nice IVs and level. The other one would be my last priority since he have a bad moveset.

Both these Laprases are great for defense and good for attacking. If you have enough candy and don't think you will hatch/catch another Lapras for a while, I see no problem powering up the second one as well. The high attack stat will make sure his CP is decent even though his IVs are low. And Lapras has high HP and defense stats already.

I would hold out a bit though, since with the current gym meta, there isn't much point in prioritizing defenders over attackers. I would probably keep buddying Snorlax if I were you.