If you want absolute perfection to dial it in you will need rear camber arms. That being said if you just did a small drop on some springs you are good to skip those for now until you get a more aggressive drop or want to start dialing in specs for road racing.
SPC camber arms will allow you to dial in a small drop. You don't need the RV6 components. Even if you did replace everything with RV6 their camber solution is complete without the SPC offering
SPC 67476 . They are sold individually so you need two some vendors like axion sell them in pairs.
It depends on how low you are planning to drop the car and if you care about setting the camber back to (as close as you can get it with) factory specs.
My car is lowered on swift springs and I have not used a rear camber kit.