1. You are dealing with high voltage wires possibly including a fibre glass core and carbon so a straight path is better than a curve and a curve is better than a right angle.
2. Insulation works fine but not if next to the exhaust.
3. Wires can run together but the insulation leaks and it will degrade performance though not cause a misfire, keep them seperated with 1/8" air between them whenever possible and support them if needed with plastic connectors / bracket / cable ties to keep them off the valve covers, accelerator cables etc. You can buy the spacers and posts in a good auto store and they keep the cables tidy.
4. They are good conductors but there is no need to make them work too hard so keep them reasonably short whilst allowing them to flow in neat curves.
5. Always terminate them in the manner described by the supplier.
You shouldn't get a misfire unless the insulation is old and cracked and dirty. However they will leak to an extent. These cables pass the current along the surface of the conductor, just under the insulating layer. Any break in the insulation will allow leakage.
What type of ignition leads are you buying?
BagusJeep lives in Bali.
1981 CJ7 258ci - Bagusjeep
1984 CJ7 258ci - Puthijeep
1981 J20 258ci - Gladys
1951 Willys CJ3A/MB/M38 - Little Willy
1995 Cherokee 4.0 - CHEROKEE