At first I was very concerned about the lack of USB-C at the Spitz AX (X3000), too. But after installing it in my RV, I think the regular around 12V is a good alternative to the more complex USB-C.
For traveling without RV, there is no difference between the Power Supplies. I would not attach a 3A device to my laptop.
For reference: Spitz AX - Install in a RV
I hope the Spitz Plus will be a great budget alternative, like the Slate Plus to the Slate AX.