I’ve just recently started to try to work on reamping with my Fractal Audio Axe FX, I reinstalled the drivers for the AF2 but SPLAT still doesn’t want to allow me to use the AF2 usb for recording, it won’t even allow me to select it. I am using a Focusrite 18i8 as an interface. The only time I got close was using ASIO4all, which causes random loud tones and is just a pain.

Anyone have any advice?

The ASIO specification does not permit hosts (SONAR in this case) to use more than one I/O driver at a time. As a result, in order to change drivers when running in ASIO driver mode both input and output drivers must be deselected prior to making a new selection.
 
It is possible to use more than one driver at a time when running in any other driver mode. Because ASIO4All is really a wrapper for WDM drivers, it can aggregate multiple drivers presenting them as a single ASIO driver to the host.
 
Some hardware manufacturers supply ASIO drivers that aggregate several of their interfaces but not interfaces from other manufacturers.

Have you tried WASAPI mode?