"1) Impedance is not resistance; it's impedance, resistance is reserved for DC current. Impedance, in regards to car audio subs ratings, is typically a nominal measure of how much an AC current is "impeded" by the load. "
Like I've already stated, in context of this discussion, the industry treats the 2 as interchangeable. If you like, I can look up an example and copy and paste it for you.
"2) 2 ohms away from a dead short is very much an overly dramatic description. You are NEVER going to get close to a dead short with a subwoofer when it's wired at 2 ohms. You WILL NEVER reach an impedance below the DCR (DC Resistance) of the voice coil, which typically is only a few tenths lower than the rated impedance in most car audio subwoofers. Also impedance typically rises in practice due to heat, box rise, inductance, etc. You definitely can't make make a blanket statement about frequency's effect on impedance when a large portion of the dynamic load is due to extremely complex EM interactions between any induced EMF and the subwoofer motor."
2 ohm's away from a dead short isn't dramatic, its a fact. In this case we're dealing with a 1 ohm load, not 2. If you would set your system up to create a 1ohm load over a 4 ohm load, then go ahead and do it. Its you system. I disagree. I would only do a 1 ohm load if I was forced to.
"3) A 2 ohm subwoofer amp is typically designed to handle the higher current associated with a lower impedance load. Unless your charging system is garbage or you bought a low quality amp it won't be overly hard on an amp. Have some faith in the engineers who designed some of the solid amps on the market today. Note: Typically it's much cheaper per watt to purchase an amp that produces solid power at lower impedances, and that power isn't just "on paper." High voltage amps tend to be a bit pricey and to maintain a similar power output at 4 ohms or higher is cost prohibitive to most consumers. I can find you a dozen affordable,reliable amps that make 2000 Watts at one ohm and handle it all day. 2000 Watts is a lot more difficult to find at 4 ohms, and you will likely be paying for it unless your willing to go with a Brazilian design."
Sorry, but a 4 ohm load is much easier on the amp than a 1 ohm load. To avoid a bunch of back and forth posts that go no where, I got some info on Crutchfields web site.
https://images.crutchfieldonline.com/ca/learningcenter/car/subwoofer_wiring/1-DVC-2-ohm-mono-low-imp.jpg
Notice the warning for 1 ohm use.
"4) As others said you seem to have the concept of parallel and series wiring backwards."
Anyone can, and will, claim anything to win an argument. I made the OP aware of my 2 word typo, and you're just going to have to be OK with it.