Yup, Marui VSR-10 is the best.
You only need ghillie if you lay down and wait a lot. For that to work, you will need a mislim game. Most of the time a head and shoulders "ghillie" is perfectly enough.
Since you said we shouldn't discuss pistols, then I won't say that an NBB like an MK23 is more suited as a sidearm.
Proper airsoft sniping is a very different playstyle to normal playing. If it's similar, then you are not sniping, you are a DM.
Practice with your gun a lot. Set it up so that on about 40 yards it shoots exactly where the crosshair is. Learn where you should aim on 30-50-60 yards. A very-very good AS sniper gun can do a grouping of 30-40cm on 70 yards. That means every shot is inside that circle. If someone says "mine is better", tell them to prove it. Measure 70 yards and place 10 shots on a target, and don't leave out stray BBs, or blame the wind, etc. Place ALL the shots inside that circle.
Anyway. You won't even shoot that grouping in a game, because the target moves, there is some wind, there is some foilage in between, you are tired, etc. You usually shoot at about 40-50 yards. Well within the range of AEGs. So sniping is mostly about surprise. Get them from an angle they don't expect. Place 3-4 shots, and leave even if you don't have a hit. Once someone with an AEG knows where you are, he will get you. Well, you can use this to lure them. Get some shots, and when they go after you, you are already in a spot you found earlier looking down your previous position. It's not easy to do this but it's an awesome feeling if you pull it off.
Don't be afraid of laying down, moving very-very slow or staying in one place for half an hour or more - and leave without a shot.
Use the heaviest BBs your gun can handle, and use the best ones you can find.
The other playstyle you can do is being a DM. A DM moves with the team, and engages the enemy about the same way as the others. Your gun shoots less, but more accurate so eventually at the same success rate. For this style - because of the minimal engagement distance - you will need a sidearm with good firepower. For a sniper an accurate and silent handgun is the best. For a DM, something that shoots a lot. GBB with spare mags, AEPs with full auto capability, even SMGs. Once I played with my sniper gun on my back on a biathlon sling and my AEG in the hand, being able to switch them - which was a pain in the ass but it was fun to have the extra accuracy and scope when needed.
You will see what works for you and for the sites you are playing. The most important is that even if you have a lot of experience with an AEG, be prepared to learn a lot before you can be a succesful sniper.