The laptops use what ASUS' calls its Active Aerodynamic System (AAS) to stay cool. This comprises a ton of air intakes, dual high-speed 12V fans, five heat pipes, and an array of four heat sinks. The heat sinks are dedicated to the CPU and GPU and the circuitry that supplies them with power, and they're made up of ultra-thin copper fins that are as slim as 0.1mm. This means more fins and a larger surface area available for heat dissipation.
Cool air is drawn in through the large openings at the top and bottom (when the lid is open) and dumped out four vents at the sides and back. The vents on the side are also angled toward the back to direct warm air away from your mousing hand.
In addition, there's something of an anti-dust system in place in the form of tunnels that catch and redirect particles outside the chassis. This helps keep the heat sinks cleaner in the long run, something that's vital to cooling performance.
The more forward location of the keyboard also means that it's further away from the main heat generating components, so it feels cooler. However, the area above the keyboard can get quite hot to touch, especially around the center.
Both laptops support NVIDIA's Optimus technology, which can automatically switch between the integrated and discrete graphics to conserve power, depending on the workload at hand. However, the GX701GX does have an additional control in the form of a so-called GPU switch. This is basically an option that lets you switch between G-Sync and Optimus modes. In the former, G-Sync is on, so the discrete GPU is active always. Conversely, if you want the automatic switching between integrated and discrete graphics, you'll need to manually enable Optimus mode.
The port layout is varies slightly between the two laptops. For starters, the ROG Zephyrus S GX531GX makes use of the sides and back, whereas the GX701GX restricts itself to just the left and right edges.
The smaller 15.6-inch model features one USB 3.1 (Gen 2) Type-C, one USB 3.1 (Gen 1) Type-C, one USB 3.1 (Gen 2) Type-A, and two USB 2.0 ports. The HDMI 2.0b port is located at the back, which may make cable management easier when outputting to an external display.
The USB-C port on the right also supports output over DisplayPort 1.2, and you can charge the notebook via USB Power Delivery if you have a compatible power bank or Type-C power adapter. This is pretty useful if you forget the power brick or want to deal with something more compact.
Like the GX531GX, the GX701GX has six USB ports as well, but the two USB 2.0 ports have been replaced by faster USB 3.1 (Gen 1) Type-A ports instead. The USB 3.1 (Gen 2) Type-C connector also supports the DisplayPort 1.4 standard instead of 1.2, and charging over Power Delivery will work as well with a 65W adapter.