Static vs Dynamic
With that out of the way let me begin. There are two types of gate-camps, static and dynamic. An example of a static gatecamp in nullsec would be drag bubbles setup inline with the various system gates with a light dictor to catch targets jumping in, usually with cloaky recons and fast ships that can GTFO if there is a hotdrop. A dynamic gate-camp would be similar except instead of anchoring bubbles you would use a cloaked dictor in drag bubble position that would decloak and drop a bubble at your desired range whenever something jumps in system. Dynamic gate-camps aren't as common since they go against the casual nature of the gate-camp, but are useful when operating in hostile space because you can go into active and passive mode at will making it much harder to counter via intel channels and roaming gangs that take your bubbles down. Think of it as the AFK cloaky version of a gate-camp.
Static gate-camps tend to have more of a "catch ALL the things!" mentality, where dynamic gate-camps are much more selective and while you might not catch small stuff like shuttles and noobships, you're more likely to catch things that matter. Anyone who has ever been on a static gate-camp in any security space can attest that unless its a heavily trafficked pipe with large amounts of stupid, the kills you get tend to dry up once your gate-camp gets made.
In highsec, while most gate-camps can probably be considered static by definition, you have the ability to move around and change the pipes and chokepoints you camp rather easily. This means as long as you have scouts and are proactive, you can move around throughout the day based on who transits where based on timezone. Additionally, you run can dynamic gate-camps by hiding in side systems or wormholes. In fact, if you're particularly motivated to probe down wormholes, Highsec-to-Highsec wormholes allow you to essentially camp two places at once or approach an enemy gangs from an unscouted direction. The amount of things you can kill is only limited to how many alts you have and how willing you are to scout. There are really only a few set routes that people can take through empire and as a result if you are willing to spend the time you can capitalize on this, which brings me to my next point.
Routing and Traffic
The entire point of gate-camps is to catch people while they're traveling. In nullsec, this usually means empire entry points, jump bridge chokepoints, and heavily trafficked pipes. Changing where you camp on the fly isn't really an option because if you're blue to the rest of the area, the places you can camp are limited to hostile entry points, so theres no real point camping a friendly jump bridge connection. Likewise, if you're operating in hostile territory, you have to deal with dodging reds.
Highsec traffic on the other hand tends to be between trade hubs and nullsec entry points. In Highsec, you can move much more freely, so its possible to camp multiple pipes at the same time if you have scouts far enough down that you can move to intercept a slow moving battleship, although this takes a fairly decent knowledge of empire autopilot routes and the willingness to scout. How much you kill is really only limited to how much you're willing to work and how many alt eyes you have. For example, if you're motivated enough, you can camp all connections going in and out of Jita, although most people are content to camp a single pipe.
This is one of the reasons I personally enjoy Highsec. I find it interesting how you're able to take a much more proactive role in getting kills through good scouting rather than just waiting for idiots to leeroy into your bubble. I enjoy the fact that you have a much bigger playground in terms of systems and regions such that having an intimate knowledge of auto-pilot routes, gate distances, and side systems can give you a distinct advantage over those who don't know such things. To me catching targets in highsec is like an elaborate game of chess, and in that regard, I prefer the mental stimulation over the adrenaline rush that other PVP areas in EVE provide.