Out of all the Electronic Warfare modules, the Target Painter is the only one that really works on NPCs, since it just increases their signature.
The others do have a slight chance to work on rats but NPCs have a tendency to cheat when it comes to EW, so it's usually not worth it.
There is indirect PvP aspects in Planetary Interaction, and soon there will be direct PvP aspects with the release of a console game called DUST514.
The indirect PvP aspect is fighting over resources. This was only turned on in some of the later patches in the Incursion. On each planet there is only a limited number of the resources in the ground, which only refill at a certain static rate. The planet will support some (unspecified) minimum amount of resource being extracted, then after that it will deteriorate. This means that too much concentration in the area will deplete the resource for all players pulling that resource out of the ground at that place.
The direct PvP will come later when the DUST514 console shooter game comes out. Exact details haven't been confirmed yet, but the base premise of it is that people playing Eve Online will be able to somehow ask players in DUST514 to somehow disrupt other Eve Online players Planetary Interaction networks.
There are usually two types of Planetary Interaction (PI) setups : Extraction and Factory setups.
With Extraction setups, PI doesn't really require any sort of ongoing ISK costs to run besides export fees of planetary products, therefore all PI here should be "profitable". In High-Sec you won't get very high extraction rates at all, and they will be highly contested, which means not very profitable on a "ISK-per-time-invested" basis. Lo-Sec can be better, but Null-Sec and Wormhole planets can be quite lucrative. There is a larger risk in transporting the PI products from these lower security areas of space though.
With Factory Setups, people can make a fair amount of ISK by making PI setups in High Sec that purely concentrate on turning lower level cheaper PI products bought from the market into higher level more expensive products. You'd need to figure out what is profitable here and what isn't as it would also be quite easy to lose a lot of money doing this if you chose the wrong products, or the sell prices of the high-end product dropped unexpectedly.
In terms of investment of training time, it doesn't take too long to get decent PI skills. Anywhere between a few days for some basic skills to a couple of months to be able to run multiple planets with high level command centres depending on how much PI you want to be involved in.
Best Answer
An Energy Vampire (aka a NOS) at it's base removes capacitor energy from the target ship and adds it to your own. But it only works if the enemy has more cap than you do, in terms of percentage. I.e. if you have 10% of your cap left, and your target has 50%, then every cycle of the NOS will transfer some of the targets cap to your own. If you have %90 cap, and your enemy has %50 cap, then no energy will be transferred, but the NOS will still cycle.
Every cycle makes the measurement of cap levels again, and cycles that don't actually transfer any cap, don't actually use any of your own cap either, so usually people just leave it on Auto-repeat and keep it going the entire time they are within range. It will only turn off if you go out of range.
So what does this mean in reality? Basically there are usually a few places where you see this used (and this doesn't cover all uses, just some of the most common I've seen) :
A ship that uses modules that rely on relatively large amounts of cap and is not cap stable without it. The NOS will be used to keep stuff going as much as possible, longer than it might have been able to without one. Examples of these modules are probably most commonly Armor Repairers, but to a lesser extent might also be MicroWarp Drives, Shield Boosters, Afterburners, Warp Disrupters. Probably others as well. Usually the tactics with such ships are to burn in close and run the repairer enough to mitigate enough damage to turn the fight in your favour. When the repairer runs your cap low, the NOS will be sucking cap back from your target that you can use to run the armor repairer.
A ship that wants some defense against Neutralisers. A Neutraliser in the right situation could remove all your cap, leaving you without the ability to run your own warp disruptor, scrambler, webber or other active modules. Usually this means it will either give them a lot easier time to escape, or it might even shut down your active resistance modules like Invulnerability Fields, making you easier to kill. Having a NOS might give you enough cap back to still run the essential modules you need even under neutraliser pressure.
PvE fits where you expect to have rats close up a lot of the time. Because of how NPC AI works, they often act as though they are at 100% capacitor all the time, so when you use a NOS on them, they will always transfer cap to you. This means you might be able to swap a Cap Recharging module or two out for something more useful if you are using a NOS.