Aside from the battery, mechanical mods have no electronics or wires. Reading the resistance needs to be done using electronics and will have to be done with an electronic PV or a multimeter.
I think that the first consideration when choosing a mech should be the body style and button location (side, pinky, bottom, etc). This is a personal preference - I like bottom button mods. You should look at pictures of different mechanicals and try to decide this for yourself. Conductivity is a consideration - you definitely want brass contacts, perhaps with silver or gold plating (I think that silver is more durable than gold and either way, you'll be disappointed when it starts to run off).
With a mechanical mod you're really just dealing with a 510 connection powered by a battery. Different models have their pluses and minuses. If you want to learn you should hit YouTube and look at
reviews of different mechanicals - it's helpful to watch people disassemble and assemble it. You can search the forums for commentary on different
devices - most popular models have dedicated threads where people will share the good, the bad, and perhaps the ugly.
Some people like to buy clones at first to get a feeling for what they like. I did my research and picked what would be considered a high-end mechanical after much deliberation. If you buy a high-end
device directly from the source you're most likely to receive quality support in case something is wrong. I'm concerned that I've become addicted to buying mechanical mods, but I don't regret anything that I've bought.
