You're going to need a significant amount of battery power to run even 200W.
Basic maths: 200(Watts needed) รท12V = 16.67Amps
So with a standard 3.7V rechargeable cell, you'd need 3 in series to achieve ~12V. Most of those discharge at about 2A, so you would need 8 of those "sets" in parallel to provide the amperage. Thats 24cells just to turn it on. Depending on setup, that may not even last long enough to be useful. You can cut some corners with high-amperage cells, or up-converting to higher voltage, but the energy consumption almost necessitates an AC power supply or a heavy battery system. I would consider all _TX form factors to be power-hungry, and designed to use with a power supply. They do offer upgradable components like RAM and Processor, but that trade off is rarely worth it in comparison.
If you're still shopping hardware, I highly recommend the micro PCs built around solid state and mobile tech. They are much more power efficient, smaller, and usually cheaper than ITX. Basically mobile hardware with desktop interface and IO. I found a dual core 2GHz, 4Gb RAM, 64Gb MMC with WIN 10 preinstalled for less than $150(US). Full HDMI, VGA, USB 3.1, USB C, with M.2 and SATA ports for HD expansion.
For power comparison, it draws like 1A (10-12W) or 1/10th the power as iTX. So running on a 12V power supply is fairly easy. 3-6 cells vs 24.
For something more graphics intensive like gaming, you would probably need something more like this one with 8Gb and dual 4K. Or step up to a legit one like this with an i9 and a GTX1650.
If you aren't fond of the cheaper Chinese and Korean brands, Asus, Lenovo, and HP make their own versions as well. There's soo many to compare, it's subjective to usage.
Also, as a personal suggestion: Slow down and proofread your posts. The typos are almost too much to understand the statements.