LGA1151 is split into two categories.
6th and 7th generation Intel will work with 100 and 200 series boards: H110, H170, H270, B250, Z170, Z270
Top CPU is the quad core i7-7700k (8 threads)
8th and 9th generation Intel will work with 300 series boards: H310, B360, B365, H370, Z370, Z390
Top CPU is the eight-core i9-9900k (16 threads), i7-9700k (8 threads) gets a mention as being an 8 core without hyperthreading. i7-8700k is a six core chip with hyperthreading.
There is a slim chance of an LGA1151 DDR3 compatible board, so yes, a DDR4/DDR5 upgrade may also be required.