The module CYBLE-416045-02 has a provision for you to connect an external crystal or any external clock signal to the watch cystal oscillator (WCO). The device port pin P0.0 can be used for wco_in and P0.1 for wco_out.
But external clock source cannot be connected to the ECO as it is internally connected in the module.
as you asked for high frequency clocks,yes there is also the possibility to do that.
You can either connect an external crystal (ECO) to pins 12.6 and 12.7 or connect an external clock to pin 0.5.