Honestly, if you can find a good vv/vw device, you can do anything a mech can do, with battery protection and constant power level. If I had it do over again, I would have started with a hana....
But, I love mechs, anyway
Mechs aren't much more than a tube that holds a battery, some sort of switch, and an atty connector. Material well make a difference in conductivity (copper being the best conductor, then brass, then ss).
Some have better switches than others. Something that will put contact in direct touch with the battery, is going to lose less voltage. If you have a magnetic switch, it is pushing the switch apart. You push the switch and it pushes your contact directly to the battery.
Some use springs, with the spring being used as part of the circuit. You lose voltage every time you throw another step in the chain, especially if that spring is made of a less conductive material.
Those are just generalizations, it depends on the mod itself and the design.
Exactly what kind of stuff are you looking for?