Congratulations on the RG550! Looks like a great player guitar, worn in and ready to rock.
From the looks of the pickup bobbins, it's most likely a Dimarzio Tone Zone, but there are less popular models with the same bobbins.
If you want to know for sure, yes, you have to take off the strings, and then unscrew the pick guard, and just look at the underside of the bridge pickup.
You don't have to remove the pickup at all, just open the guitar up and take a look. It should either have a sticker, or a stamp into the under side of the pickup that tells you the model number.
From there just go to the Dimarzio site and see which model you have by matching the number (Tone Zone is DP 155).
As for the difference between the different V humbucker pickups (Ibanez version of the Dimarzio) they are made specifically for neck and bridge sounds, so they don't sound the same.
I usually always replace my stock V pickups in all the early RG models I have, usually with Dimarzios (My favorite is the Tone Zone or PAF Pro, but I have other models in other guitars so I can get different sounds from all of them). The V's don't sound all that bad, but you can get a wider variety of sounds by using different models of Dimarzios. More versatile.
Enjoy your first Ibanez RG, you got one of the best ones! (in my opinion