"this is false in a single voice coil parallel setup correct?"
Current will still flow as long as there's still path. Series wiring requires current to flow through each component before "moving on" to the next one, but parallel wiring doesn't need that, as each component is a separate "arm" that all see the same voltage from the circuit. The attached picture below might show it a little better, sorry it's kinda sh1tty, I spent like 3 minutes on it. these symbols: -/\/\- are resistors representing speakers in this case.
"the speakers only share part of the port. port starts 1 inch from airspace and combine in the center as a 2 inch port area. Or does this still mean shared airspace?
Don't think about each speaker seeing part of the port. The enclosure will always behave a certain way regardless of how many speakers or what type of speakers you have in it. The response of the speaker can be influenced by the enclosure it's in, but not the other way around. Consider this: let's say one of the speakers dies in your design. The other speaker continues to move, and as the air on one side of the enclosure is compressed and rarefied, it creates a sympathetic resonance with the air mass inside the port. That air mass, as it moves, then creates a sympathetic resonance with the opening into the side with the dead speaker. All areas of the enclosure are still being used. If you're unfamiliar with how ports work; it's in the same way as when you blow over the top of a bottle and hear a tone. It only requires a small amount of energy blowing over the top of the bottle opening (which you could consider the port opening) to make the air in the neck of the bottle rapidly move up and down, so it's that block of air in the neck of the bottle itself that's acting like a speaker.
"so like the port is a folded horn port design, since the port now goes 1 inch for half the port to 2 inches wide the rest of the way"
Even if we were to imagine that the other side of the enclosure was somehow blocked off, you would still be left with a much larger area of port with the same length, which would raise tuning - probably by a lot. Folded horns (and true transmission lines) use much more complicated impedance transform to produce their output than just expanding a vent, as there isn't a discrete definition of "port" areas and "enclosure" areas, its a continuous transform that requires a lot of math to get right, lol.
"I can put a separator in the center of the 2 inch port so each one has their own true space"
That would work to fully separate the two and make them independent. Unless you're really worried about blowing speakers, it's not required. I guess if you can add it in and it won't take much extra effort than it's worth it.
"Does it really matter? I have seen bass builds that use that port design, does it not work for full range?"
Nope, it should work well. At frequencies an octave or two above port tuning the speaker acts exactly the same as it would in a sealed enclosure.
More question from your edited post:
"Winisd predicts I hit about 5mm of excursion at about 100 hz and 47 hz. xmech is 11.5mm (right?) Its good that speakers ride at about xmax at rms right?"
Excursion in a sealed
enclosure will grow larger and larger the lower in frequency you go. Theoretically, to maintain the same amplitude an octave lower than a certain frequency, you need 4x the excursion, so for example if you wanted the same SPL at 30hz and 60hz, and at 60hz the excursion was 5mm, you'd need 20mm of excursion at 30hz. Vented
enclosures fix this by reducing excursion around the tuning frequency substantially (think back to the bottle example: it only requires a small amount of air movement over the top of the bottle to produce a loud tone from the air in the neck of the bottle). The downside is that the excursion characteristic when plotted by frequency is exactly what you are seeing: excursion shoots up right above and below tuning. That's usually a fair tradeoff though, as excursion is still much lower than a sealed enclosure given the same output. It's not generally a good idea to design for a lot of excursion, but unless you plan on listening to sine waves at full blast around those excursion peaks it's shouldn't be an issue. On music you'll be fine. Still, I highly recommend you use a high-pass filter no lower than 40hz to protect the speaker from bottoming out on low notes.
"Is that what the young kids call slammin at those frequencies?"
Lord I hope not.
"Idk whether I should tune lower. Tuning lower causes very close to xmech failure at 100 hz."
For those speakers: don't tune lower. You'll just loose output where it's actually important. Trying to play low bass from a couple (relatively) small speakers outdoors is like farting in the wind.
"and how much does port area affect excursion? in winisd the excursion doesnt change with port area change, I assume in real world it does affect it."
It doesn't, at least not in your scenario. Vents with too small an area can act as aperiodic dampers, and there's a good case for larger ports and especially flared ports with regards to increasing port efficiency, but for something like your project it won't be a major thing. You've got PLENTY of port area, you could probably reduce the area by half and shrink the port by the appropriate amount if you wanted to. Keep vent velocity below about 33m/s (100ft/sec) and you'll be fine. WinISD should graph vent velocity for you. If it doesn't make sure you have the "sd" parameter filled in in the TSP section. sd is radiating (cone) area.