This is the lead clip system I use which as you can see has a few modifications. Like all the lead systems I use they are put together so that they can come apart safely, work efficiently and without unnecessarily dumping leads.
I use this lead system over bottoms that are clean to light weed/detritus. The lead will neatly bury itself while the clip & rig tube rest on the upper layers. The lead is effectively hidden while the rig lays flat. To help ensure this, always trap the line when the lead hits the water and follow the lead down with the rod tip.
The clip is used without the peg to hold the rig swivel, instead the clip is lightly squeezed until it grips just enough to set the hook using the weight of the lead. If a carp tries to use the lead as leverage to dislodge the hook then the clip will pull free of the rig swivel. This has the effect of turning the lead system into a running rig negating any further attempts to use the lead to shake the hook free and avoiding unnecessarily dumping the lead. The clip has also been cut down and drilled out. This helps it slide up and down the leader/mainline far better and it also ensures that should the lead get snagged it can easily pull free.
The distance cast and the nature of the bottom determine the lead type and weight. Torpedo leads cast furthest and so can be used in smaller sizes. They lift out of weed easily but they will also bury just as easily, however they are less likely to snag. Flat leads have the shortest cast but will rest on top of weed/detritus and not bury as easily, they also lift off the bottom well. Pear leads cast well and can bury easily in weed especially if used in larger sizes, they are also more prone to snagging. However for clean, silty/detritus or light weed they work very well.
What you want is a balance between the distance of the cast and the effectiveness of the rig. The lighter the lead the less chance of a tangle on the cast and they do not bury as much giving you a better chance of good presentation. They also make far less disturbance when hitting the water. The drawback is that they might not be heavy enough to set the hook. To help overcome this it's best to ensure that the leader is fully down and the line is bedded in well. This will give the lead system more grip and vastly improve the hooking ratio.
If you need to use a bigger lead to set the hook then more time must be spent looking for a spot to place it on. As ever a few casts first with a light lead, dragging it back through the swim can tell you all you need to know and help you with your choice.