I recently ordered some new pc parts and was hoping to use my Z370-p board that's brand new will there be any issues using it with Intel Core i9 9900K 3.6 GHz Processor, Asus ROG STRIX GeForce RTX 2080 Ti 11GB OC Graphics Card, I also bought Corsair 850 Watt RM850x Fully Modular ATX Power Supply as I don't think my Corsair sv550 be enough to run those parts.
It would be OK. But if you are paying that much of money why you wouldn't buy an Asus-Z390 ROG instead. The price difference is really not that much and ROG have some advantages (not just a newer chipset) from what you have bought, I believe money is not an issue.
and buy a good CPU cooler. 9700 and 9900 really runs hot. Liquid cooler or Noctua NH-D15 recommended. And a big case to fit all.
Reason I was planning to use z370 I've had it for 2 yrs and never got to use it I was sent the wrong motherboard for my i5 7400 and was allowed to keep the board. I could buy z390 if needed is the mr850x strong enough to run this with coolers also do I have to look into gpu cooling? I don't care too much about overclocking just want my system to last. I'm using thermaltake tower 900.