Curious the hive-mind's thoughts on a 12v electrical project I'm considering.

New owner of a Jayco 377RLBH fifth wheel; no kids here so I am working on setting up the bunkhouse as an office space. I have an LED computer monitor and laptop that both run on 19.5v that I would like to be able to wire into the 12v system so as to maximize my future options for sites without electricity (the unit came with the 190W panel and GoPower controller, so there is easy expansion capability there on the solar and battery side.)

The monitor draws 4.7A and the power supply for the laptop has an output rating of 9.23A. I'm assuming the difference in voltage rating (19V for one and 19.5V for the other) is negligible.

My thought is I could wire into one of the empty 12v circuits on the power distribution panel, not one of the "top 10" that is for low current operations. https://www.progressivedyn.com/rv/power-centers/4500-series/

The voltage conversion would be done with a buck transformer, e.g. https://www.amazon.com/uxcell-Converter-Regulator-Transformer-Waterproof/dp/B01MQJ4IJJ/ref=sr_1_3?dchild=1&keywords=12v to 19v 20a&qid=1612331672&s=electronics&sr=1-3

As I understand it, upping the voltage drops the resulting current (?), so the question is, would a 20A circuit be acceptable here or does it need to be 30A? It looks like I have one 30A circuit open on the distributor, but more 20A space.

Also more generally, is there any good way to monitor total current draw on the 12v system?

Is my thinking here in line at all with reality or am I way off? Jayco obviously advises against any "alterations" but it seems to me that this is akin to adding a circuit to any other breaker box, so long as you don't overload the total capacity.