Yes, all the channels (8 input/8output) are working! You can record DI from the guitar/mic as well as processed signal, playback sound, reamp...
I don't know how well you know this stuff, if you're new to this here are some simple steps to make it work:
Setting it up with jack is the same as any other usb sound interface with Ubuntu Studio Controls. If you want it to be your master device, set Jack Master Device to USB Jack Master and USB device that should be master to HELIX. If you check Bridge USB Devices to Jack when Plugged In, you'll be able to see it in Patchage and make the connections.
Alsa focuses on the lower level audio, handling soundcards but also midi. Jack and Pulseaudio both use alsa as backend (most likely in your case). Pulseaudio is used for standard applications but is not suited for real-time use. A lot of applications like Firefox don't work with Jack (check out Pulse-Jack bridge to run Pulseaudio and Jack at the same time). Jack allows you to run audio applications with very low latency.
A good ressource to check out: https://help.ubuntu.com/community/UbuntuStudio/AudioHandbook ;)
Also, about low-latency vs generic kernel, low-latency used to work better for me but nowadays generic is definitely better the way ubuntu studio sets it up.
Hope this helps :)