Quick video to show you how to modify the command line arguments for Apex Legends to allow for an uncapped GPU framerate.
By default this is capped at 144fps.
I uncapped it, and did some testing with LOW settings with the Intel i9-9900K processor along with the NVidia GeForce RTX 2080 Super graphics card.
TLDR; It seems that I get between 200-300 fps on this rig for the game on LOW settings. Just for comparison with Fortnite I generally can get between 400-450 with the same hardware. Apex Legends seems to be a bit more taxing on the hardware even on the lowest graphic settings.
Hope this helps!
HP Omen Obelisk Core i9-9900K
NVidia GeForce RTX 2080 Super
Intel i9-9900K Processor
Intel Core i9-9900K Processor
NVIDIA GeForce RTX 2080 Super 8GB
HyperX 32 GB RAM
1 TB Intel NVMe SSD