Unless you are playing at 4k and even at 4k you will be severely bottle necked with a 6700k. a 3090 gpu requires at a minimum 2 8pin PCIe power cables from the PSU in addition to the power from the video card slot. You need a very robust PSU to run a 3090 GPU without issues. I could try to help determine if your system is capable with more detailed information on your systems current PSU. Please include the brand, model number, and wattage of the PSU.
It would be dependent on your power supply as far as having enough, it takes a lot of juice.
While the 6700k might feed it if it was overclocked, out of the box speed will likely not do. The 3090 would be waiting on data, and making a card wait is when it will perform badly.