Hi niallmack!
This is my personal opinion only but I hope it could help you with your choices.
From your picks, it occur to me that you are looking for a computer or a device capable of running Illustrator for pure illustration purpose. Furthermore, what you are looking for isn’t a high-end model but a budget device falling in the range of $1200 USD or under.
While it depends a lot on the type of work you are thinking of doing with this new device, from my experience, the three picks above will not be able to fully satisfy your needs.
First, no matter if it’s illustration or design work, a device capable of processing a large canvas is better. You may think you can make-do with drawing illustrations on a smaller canvas. However, by doing so, you will risk two things: First, you might not be able to catch a good look at your illustration in overall as the smaller your canvas is, the more difficult it is for you to catch all of the details and the general feeling from your illustration. And second, you will lose a lot of details and your illustration will be greatly limited due to the small canvas.
Second, choosing a low- to mid-end device at this stage might not worth the efforts and troubles unless you are a hobbyist and not someone who is looking to work professionally soon. As a professional, more than frequently, we have to work with exceptionally highly detailed images and illustrations. Recently, 4K images have become the new standard (as monitors capable of processing 4K images are becoming widely available) and in many cases (depending on your field), it’s not rare to work with 8K or 16K images. Illustrations and images at these resolution, while can be viewed on mid-end devices, will completely freeze your computer when put into an image processing software such as Photoshop or Illustrator. As such, you should consider finding a high-end device if you are thinking of pursuing this field professionally. A device with a minimum of 32-GB RAM is recommended for professional work, If you are thinking of doing high-res video editing also then at least 64-GB RAM and a dedicated GPU (Graphic Card if you prefer it this way) is required (and believe me, you will still experience lags and such even with machines at this range). 8-GB RAM will only be capable of processing simple images at 1080p at most and will start to encounter problems at higher resolution.
Third, I believe you are putting too much weights on the general performance of the device and not on some other aspects that an illustrator or a designer need to pay attention to. One of the aspects I’m talking about is the quality of the display of your device. As a designer (and a concept artist), I highly value the color accuracy and the high-resolution image processing power of my display. While some might argue that you can adjust the color by yourself, a good display with high color accuracy will greatly enhance the quality of your work even when your work is designed for printing or digital exhibiting. The three picks you’ve listed above are designed for general audiences and convenience usages and are not optimized for creative works. As such, in general, their displays’ capabilities is limited and should not be chosen.
I have a bit of question though, why do you need the drawing capability of a touch screen? While it’s certainly more convenient to draw directly on the screen, depending on the type of your illustration work, drawing using a mouse is also a viable approach. Personally, I’ve only gotten my drawing tablet recently and for the last few years (ever since I begin doing designs), a good mouse has always been my companion. If your illustrations are not overly complicated, I would recommend sacrificing the touch screen for a better device at the same price range.
Above are my personal opinions and some experiences. I hope they could help you to get a clearer image of what you are dealing with and could help you to find a better choice.