I’m answering here rather than in the e-mail you sent me. First, I suggest you go to my smelly water page using the link at the left side of the Tank topics index, and do the simple troubleshooting sequence toward the bottom of the page.
Most people who have smelly water have the same issue, and a powered anode will solve it. But a few have some other issue, and it’s better to find out which is which before spending money.
If you decide you need a powered anode, get just one and plug the other port with a 3/4-inch galvanized plug. Both sacrificial anodes need to be removed or you’ll still have odor.
With the softener, options 2 and 3 are likely to cause you grief, while option 4 will just be temporary. You’ll have exactly the same problem with a new water heater (option 6).
If the anodes are flush with or above the cover, SKU15 might serve you. If recessed below the cover, then SKU27.