Yes, The NEMA reference is the frame size. It determines the size and location of the mounting holes. Those dimensions also constrain the mechanical diameter of the motor.
Length is the other parameter. For NEMA 17 sizes, you typically have single stack (34mm), double stack (40mm) and triple stack(48mm). There are larger ones too. Greater length translates to more torque in the same frame size.
However, there is a good reason to not use longer motors that needed though. Rotor inertia. You need sufficient torque to drive the load + some headroom, but not an excessive amount. Longer motors have more inertia and take longer to change direction. They also tend to have stronger resonances. These are not a desirable characteristics in a 3D printer which requires high acceleration and deceleration.
Low inductance and low rotor inertia are the most important parameters for a motor used in 3D printing applications…
They might work, they might not. When you go to NEMA 11, the torque is really low. You need enough to overcome any parasitic drag in the mechanism. You also need enough to overcome the inertia of the machine itself (which is quite low in a Kossel design).
The Kossel mini apex brackets are drilled for NEMA 17 frame motors anyway…
The site you linked has a lot of misspellings, typos, and generally really bad. Do not source your critical parts on the cheap with questionable online retailers. At that price point, it looks like you might get more headaches than actual results. Get your critical moving parts from reputable and reliable sources. That being said, Linear bearings are very important but the cheap Chinese bearings (with a little manual TLC on your own) is good enough to last a long time. Electronics, you should buy a genuine Arduino mega or go for a Rambo or other genuine electronics. The cheap arduino megas are not built for durability and its very likely to break on you (like things browning out or fire during 3d printing.) and cost you a ton more in the long run.
