2) yes buy the EVO 212
3) the speed difference between those drives is huge in benchmarks. In real world usage the speed difference is more like 10%. I would buy the 860 Evo. Second thought I would buy a 500GB Crucial MX 500 as it's almost as fast as the 860 Evo but cheaper.
I will go for i5-8600K. I will also go for 500GB Crucial MX 500 instead of Evo.
On the MB front since I am not going for M2 ssd and neither I am overclocking I will go for H310 MB. However in case I decide to go for a better board can you recommend me one hat is better than H310 but not as expensive as Z390 series. (Something in the middle)
I have a fondness for MSI so I'm going to say the MSI B360 Gaming Plus. The Asrock B360M Pro4 is also well regarded. The Gigabyte B360 Aorus Gaming 3 is another option. The Asus ROG Strix B360-F Gaming would also do the job.
Any of those boards would work for your build.