Capture Hierarchy- using global power pins for signal nets?

Off-page connectors carry nets (names) between schematic pages within the same schematic folder.
Global Power symbols are used to make power nets globally across the schematic design.
Off page connectors and global power symbols are two different types of symbols, they can’t be replaced from design cache. So, you will have to do it manually.

Also, I want to understand if there is some particular requirement due to which you want to use place ground symbols instead of off page connectors.

I'm considering it because we are using the block diagram primarily to be able to flow the RF flow. If I have to add ports for digital controls it will really clutter the block diagram. 

I'm considering it because we are using the block diagram primarily to be able to flow the RF flow. If I have to add ports for digital controls it will really clutter the block diagram. 

If you place ground symbols instead of ports in a hierarchical block, the hierarchical pins will not get generated. This is because hierarchical pins are used to connect the ports of a hierarchical block to the ports of its parent block, and if there are no ports to connect, there will be no hierarchical pins.
Hierarchical ports and hierarchical pins are used to connect the different levels of a hierarchical block to each other.

I use this feature mentioned by Vishwajeet for local GND's,  such as single point ground,s then create a net short component and bring them out through the hierarchy using the ports.