Schmalle

Helix is a USB sound device aka sound card. It's headphone jack doesn't support mic in from headsets. On Windows 10 click on the volume icon on the right side of the task bar. Click on the arrow on the right top to select the audio device. This arrow only appears if your system senses multiple sound devices.

The amp's FX loop supposedly has bypass according to https://www.jrrshop.com/panama-fuego-15-head-amp-figure-mango You might investigate whether that's true and if that might cause the problem.

No. It depends on the strength of the alternating electromagnetic fields that are introducing noise. Longer cables only increase the probability of picking up noise by such sources.

As stated in the thread you started TRS vs TS has no effect on sound. It only prevents added noise.

When linking the HX Stomp with the Headrush a TRS cable prohibits added noise along the cable caused by electromagnetic fields. It also brings the possibility to lift ground which eliminates hum introduced by ground loops. There are no settings to enable/disable this.Technically it's always on, but it has no effect on TS cables since the ring is shorted to ground in that case. TS vs TRS does not change the sound as stated by @rd2rk.

To communicate my observation as clear as possible: the only thing I had to adjust to replicate the behavior you described was to slightly adjust either the HX volume knob or the amps gain knob. I wish you a successful search!

Are 4 cables connected like this? 1. guitar -> HX input L 2. HX send -> amp input (or pre in) 3. amp effects loop send -> HX return L 4. HX out L -> amp effects loop return

I had a look at the patch and could replicate the phenomenon. It's gain staging. The way you have set the distortion is with boosted mids but less bass and treble. Whether the engaged distortion sounds louder or less loud depends on how close the clean amp is to saturation levels. The mid scoop of the amp's tone stack will equalize/lower the mid boost of the distortion pedal. Depending on whether the input stage of the amp gets into saturation it reacts differently to this mid scoop: Set it on the edge of breakup and the mids saturation level is lowered, but not the mids volume level. Set it clean with headroom and the mids volume level is lowered.

Here is a great resource on equalization.

Title says HX Effects.

Export the patch in HX Edit and attach the file here in a post.

No idea, but if you post a patch we might further investigate. Which mode do you use? Stomp, scroll, preset, snapshot?

Guitar volume, tone, split pickup and loose connection come to mind as possible causes.

IRs are usually normalized so that they are (roughly) as loud as they can get. The AxeFx cab block default level is 0dB.