It would be line level so that's not the optimal signal, but there are also other considerations like turning off the cabinet emulation in AmpliTube because you are sending your signal into an amp which already has a limited range which then outputs to a cabinet which you don't want to "double emulate" further coloring the sound while also not being full range. The best practice is to output to something that is full range like a powered speaker, PA, or mixer attached to full range speakers.
You can see the output impedance, etc for the different outputs here on the AXE I/O Specs page:
https://www.ikmultimedia.com/products/a ... hp?p=specs so you might want to check what is best suited for your amplifier's input between the 1/2 and 3/4 differently specs.