You have a very powerful PC, you can mine with both 1080ti cards, and with your CPU too, this threadripper is awesome
I suggest you to download nicehash first, and mine with the app they provide, it's easy to start and you will mine with GPU + CPU
https://www.nicehash.com/download-centerYou can decrease the power limit of your 1080tis because this card is a very power hungry, I suggest you to see on youtube a good overclock and undervolt to achieve maximum efficiency
But about the question of Gaming + Mining at the same time, no, you'll not do this at the same time, because both situations will consume resources of CPU + GPU, and will cause crash, freeze screen etc
Only with some very light games you can use at the same time of mining, but will cost resources too, decreasing the hashrate of mining and FPS when you are playing