@Itti8899 The resulting refresh rate of your ROG Phone 5 display will be decided by the lowest value in your setup, which is 60 Hz using the Avermedia GC513.
Since the CU4K30 supports 144 Hz passthrough at 2K and 240 Hz at 1080p, you should be able to play games on your ROG Phone 5 at 144 Hz with the capture card connected.