Couple of different questions here:
Gaming Laptop: Mobile processors, mobile GPUs. Some mobile GPUs are slightly disabled full desktop GPUs running at a lower clock frequency. Some of the available processors are nearly as fast as their desktop counterparts, and starting this generation. Intel is offering a few actual desktop CPUs for mobile.
NUC: A Nuc is essentially a laptop without a battery, screen, keyboard/mouse. These are extremely portable if you have carry wireless peripherals. You can even get a USB display or at least a very small display to carry around.
SFF - Small form factor computers are available. These are usually a pairing of a laptop CPU with a discrete desktop GPU. Not sure I know of any recent ones, not much of a...