I guess you're talking about a bolt rig.
The idea is; a weight sufficient to pull the hook home is set as close to the hook as possible. To maximise this, you would usually use a bait that allows the hook point to be clear.
In the UK, we are often not allowed to use a hooklink shorter than 12" because it can snap easier and also has the potential to cause mouth damage to the fish.
Without a doubt, a shorter hooklink leads to more hooked fish, with a length of 2-3" being ideal. There needs to be a little room for movement so a fish can pick up the bait without feeling the weight. Once inside the mouth, the sooner the hookpoint catches in the mouth, the better. This causes the fish to bolt (hence the name) and the hook is pulled home against the weight.
Mounting the bait on a hair rig is the perfect partner to this presentation, or if the bait is hooked directly, the point must be clear of the bait so it can prick the mouth of the fish.
A weight that is concentrated is usually better for this method. A sphere is the ideal shape, but some use a square-shaped lead as it stays still on the bottom better. Normal bomb-shaped leads are pretty good as well, but a spiral or flat lead would mainly be used where there is a high concentration of fish and you need the line pinned to the bottom to stop line bites.
River fishing is another area where you might use spiral or flat leads, in a bid to combat the current.
When fishing a bolt rig, you must
hold onto the rod, as the fish will tear off once hooked. The bites are what British carp anglers call screamers! Another alternative is to use a very soft rod, and set it at an angle to the water, in fact almost parallel to the bank, so the rod bends as a fish takes.
I would suggest that the fish in your waters are not so heavily fished for that you need to use a bolt rig. A simple running leger rig is perfectly acceptable, but the fish will need a bit of free line to give a decent bite.
Having the line running through a spiral or flat lead can cause resistance to a taking fish, which will then drop the bait. Swap to a bomb, where the line runs through a swivel at the top. This will allow the fish to take the bait with confidence, thus giving a better bite.
The best step to take if the fish are becoming wary of baits is to swap to a hair rig. This allows the fish to take the bait, but when they reject it, the hook stays inside the mouth, and they give the bite as they try to move off.
Good that you're thinking so deeply about your fishing