From PC World magazine
Z370 motherboards are the gold standard, built for enthusiast PCs. These are the only Intel motherboards that support CPU and memory overclocking (if you have an unlocked K-series chip), or handle gaming rigs with multiple graphics cards, at least until Z390 boards become available. They’re loaded with the most PCI-E lanes, potential USB ports and RAID storage options. As the flagship chipset, Z370 also offers the most high-speed I/O lanes. More HSIO lanes let board makers divvy out more features, like NVMe SSD connections and SuperSpeed USB ports, as they see fit.
H370 motherboards are only a notch below Z370, and perfect for people who don’t like to tinker. These boards don’t support overclocking, multiple graphics card setups, or some of the more exotic Intel Rapid Storage Technology features. Other than those niche enthusiast features, and some differences in USB 3.1 support, H370 largely mirrors Z370.