Id recommend the upgrades less the 3d printed case found on page 3 of this guide. Changing the fans out will change the noise dramatically. My s9 is able to run in any room of my house with the sound equivalent to a large box fan or a bathroom fan. If im not in the room with it i dont hear it.

The future of space heaters pdf.

As for other questions - i think if you are using them for heat, id run them in braiins until the halving. Then id prolly solo mine until they die.