For those who may read this post in the future, here are some tips to get UART1 working:
I have got the UART1 working on the Raspberry Pi header to send and receive AT commands to the cellular chips. I am using an external microcontroller to talk UART to both the WP and HL chips. There is a level shifter on the mangOH Red board for the RPi header, so this is the reason I am using it (CF3 modules are 1.8V, but my uC is 3.3). David will have his board soon that will be able to connect to the IoT slot and use the UART on that connector. I did not have to configure the WP or HL chip to get UART1 working on RPi header. On the WP chip, when I type at!mapuart?, I get 1,16, I think this was the configuration when I first got the chip. This says UART1 is configured for AT and UART2 is for console. I also had to change the UART settings on my microcontroller. I could not find much information about the settings online but the most important one was parity bit set to none. When using the HL chip, since I am only using 2 wire UART, I had to tie the RTS and CTS together. The HL chip would not respond without this. The WP chip did not require tying RTS and CTS together for some reason. Also if sending AT commands to these chips with a microcontroller, keep in mind the cellular chip might echo your command back to you. This can be turned on and off via ATE0/1 command.