I got the standard size paddle - I also have a paddle from another brand with a larger 96 in² area. I find Nixy's size easier to handle. With the larger paddle the blade tends to move sideways when I'm pulling it through the water which isn't happening for me with the Nixy paddle.
One of my shoulders gets strained if I'm too hard on it. I read that a smaller paddle, a more flexible shaft, and a shorter length would help with that, and it seems to hold up so far. That's why I picked the 3k carbon, to get a little more flexibility.
The pieces fit together nicely - there is no looseness at all in either connection.