To get back to your sound card question. As others have said, yes, the helix is basically a big soundcard, you don't need any monitors if you don't want. The helix will play in your computer as soon you select it as an input.
Using a headphone you can select in your computer the helix as output too if you want, so there is no need of input monitoring DAW, you ear the guitar all the time, and you get the sound from the computer too... just using USB
If you have monitors or simple speakers already, use them as output for your computer, the helix will pass through them in same time that your backing tracks.
I have a sound card i used for acoustic and vocal recording, it became obsolete with the helix, I can plug a mic in same time than an acoustic guitar, and even an other guitar if i wanted.
Problem solved !!!
It toke a while and the help of line 6 support.
The problem is CCtoggle have both dim and lit value of the footswich set to 127 to send info. But when selecting a patch helix send the info of the status of the footswitch value, and by so, send a trigger to logic, in fact all the info : stop, play, record, go back and cancel last record. It turns out logic start playing but i did notice a red flash like he start record but cancel...
The answer is instead of using CCtoggles, using MIDI CC, all works fine now.
olivierJez's post in Newb questions about helix was marked as the answer