audio issues - loud volume / hissing / static issues

I recently ordered a head unit for my Honda CRV-2012 (yesterday). I installed it and thing seem ok ! I had the model that has an external subwoofer, but not a navigation system.

1)  I noticed that the base volume is very loud when enabling the AMP. Is there anything to tone down the base volume ? I basically need to keep it on volume setting 1-2. I tried playing with the equalizer a bit, but I’m hoping that there is a gain setting somewhere. I had to turn on the amp option from settings to get any kind of audio.

2) There is some static / background noise all the time in the speaker (sound like mild interference). Do you have any suggestions ?

3) The white / red audio cables that come with the harness - do I need to plug them into the output of the head unit ? I did not, and I still get sound. It is a bit confusing. I also tried plugging them in - it does not make any difference.

4) I tried taking the side mounting helper bracket from the original car stereo to install them onto this unit, but they do not align properly.. how do you suggest fixing it ? The unit currently only holds onto the 4 clips that mount to the screen, but I would have liked to have the additional brackets.

I tried going in factory settings and changing the mixing level for different sources.. bringing down from 5 to 1..
Any help is appreciated, since this issue is annoying enough to return the unit, if I cannot find a workaround.
I have the same static hiss noise problem with rca output,

any recommendations for how to fix it ?

@admin, please share the motherboard technical schematics or drawings then maybe i can do some modification on the parts to fix it.
after some more digging, it looks like my CRV model (the one without navigation, but with an extra subwoofer) has an external amp, which means that the sounds gets amped twice.. that might explain it.. Joying, any ideas around this ?

Some people are recommending a line out converter, or passing wires directly to bypass the external amp, but that sound like a lot of extra work that I did not sign up for, nor do I have the expertise to do..

Otherwise, I like the unit - but the hissing noise drives me nuts.. I'm not sure I want to live with it if there is no easy option.
Following. I have all of these issues with JY-MO005N3N on my 2009 Mazda 6 GH with Bose stereo. I think the gain being pushed to the amp is amplifying the noise floor like you said. There is an option in the factory settings to balance the different inputs, but I dropped all of these to zero and it is still too loud. Need a way to turn it down, or at least clean up the hiss/wireless interference.
Joying Head Unit: JY-MO005N3N
Firmware: OPM2.171019.012
Vehicle: Mazda 6 GH 2009
Location: Australia (RHD)