Good, I think they work with 2.1v
Modules are really 1.8v 5-5-5 but thanks to Corsairs "handpicking" they raise specs and sell it as 2.1v 4-4-4. Why SPD/auto dont work. You need something like EPP A Quick Look at Enhanced Performance Profiles (EPP) Memory
Should only be important with timings, voltage. Rest of the settings are just fine-tuning, chipset/Gigabyte defaults.
Dont overclock when stress testing? You should stress test a lot when overclocking but not now with memtest86+ since trying to find out if ram is working under default conditions. Any change will in theory require you to start all over - why oc´ing is fun
Prime95/Orthos blend is stress testing memory, memtest86 is just checking.