Does not need to be matched entirely,,, DOES need to charge to, and be at, the same voltage when you connect up. I do this all the time, with a 13s 20 ah, and a 13s 13 ah pack. One pack is a year and a half older than the other, and totally different brand. No problems.
Yes,, unless you do some fancy wiring, you will need to unplug them to charge separately. Whoop de do.
You can run one pack, then run the other. Or you can parallel them for the whole ride. If your one pack is very adequate in size, there is little sag under load, then not a pressing reason to combine them for the ride.
But in most cases, you do have some very noticeable sag under load, and combining the packs results in a lot less. This sag is an indication that your cells are working hard,, and by combining the packs, you take the strain off your cells. This is Always good..
So go ahead and parallel those packs. All you need is a Y cable.
The exception, is the closed system batteries they talk about on that falco website. But others, you can just parallel them if they charge to the same voltage. Even different chemistries.