All things Volvo body and electrical!
I simply ran my Eaton 12V output to a fuse box with a 24V relay in place of the 12V relay. So you use 24V signal to turn on the relay but you only run 12V through the power side of the relay. That then distributed to the individually fused circuits.
You will end up spending $700 quickly in burnt up 24/12V converters etc. I have gone through so many over the years it’s crazy. I have tried expensive ones and cheap ones. They all seem to fail eventually. The Eaton is rock solid though. I will say I have a pair of Pyles in my Unimog U1300L that have been reliable.
Also, you will find the eatons on Ebay unused. I found a pair with a make offer listing. I got two of them for less than $800 new and sealed in original package.
If direct-conversion high-current no-12V-battery is your goal, then yes, that Eaton looks like a fine approach, and I generally agree that it's better to spend money on products that have been through thorough testing and certification in harsh environments than trying to go cheap. Youz payz in the end.