Nothing really. Whole different power envelope.
7700K is only a quad core though, the H class CPUs from Intel 11th gen are 8 cores for example, so double the throughput, at still decent clock speeds. At least briefly.
Probably the biggest chips you can get. 12th gen are a mix of Performance Cores and Efficiency Cores. So a Hex core plus 8 efficiency cores.
Laptop i9 just tend to clock higher. Any of the HK variants are overclockable and generally come in very premium laptops with heavy cooling and GPUs.
There are also the Ryzen 6000 chips. The Ryzen 7 and 9 would be quite power efficient and high core count as well.