You can unlock more FPS in apex legends beyond your monitor's refresh rate by completely turning off V-Sync. If you simply turn off V-Sync in the game, it will actually default to Windows 10's DWM V-Sync which hard caps your FPS at your monitor's refresh rate.
The trick is to use NVidia's control panel and set the V-Sync to off. Then in the Apex Legends Graphics settings, select any V-sync option (which will be overwritten with Nvidia's V-Sync off).
This is a clever way to bypass both the in-game V-Sync and Windows 10's awful forced Vertical Refresh.
I was able to run over 300 FPS in the Range at 1080p.