Ho Logan and Welcome to the Forum
You need to determine if the H115i is in fact operational. 100C at idle is definitely too hot so don't use it till fixed.
Do you hear a slight hum from the pump and that the Fans are operational.?
The H115i is a capable 280mm AIO and good for Overclocking. Changing to AIR will not get you better Thermals.
Check your core voltage in Bios.
Is the system still at stock frequency.?
Describe how you installed the unit and what thermal paste was used.
List the rest of your system specs?