Wacom is probably the safest option. I wasn't sure about using one so bought this model.

https://www.amazon.co.uk/Hanvon-ArtM.../dp/B003W28XTI

They are pretty high spec but seem to have been dropped in the UK. My feelings are that the importers priced it based in similar featured waycom tablets. I found one going cheap in a very dusty box. The same model and others are available under different brand names and the amazon reviews give a good idea of what people think of them. Only problem I had a couple of weeks ago is that our new puppy ate the 2 pens mine came with. Not available in the UK now. Could import from China but found some one in Spain who was selling a damage new tablet so I made an offer for the pens.

The first thing to think about is aspect ratio. I assume windows can do the same as I can on linux. Map a specific area of the tablet to the whole screen. My tablet didn't match the 16:9 ratio of my monitor. Fixing that reduces the area of the tablet that is active. If some one buys a tablet with a 16:9 aspect ratio and they then need to use it on a 16x10 monitor the same thing will happen. I found that trying to use it without the aspect ratio being corrected was pretty difficult.

The other thing is how much movement to sweep over an entire image on the screen. At some point it takes whole arm and wrist co ordination to track any shape. A mouse is mostly wrist and some fore arm. A bigger sweep means more fore arm and maybe whole arm movement. This can be tricky to master. Available desk space comes into size as well. To be honest I found myself using both the tablet and the mouse.

Where tablets do score is pressure and tilt sensitivity particularly pressure. Personally I wouldn't buy one without both but haven't used tilt much.

Yet another is clicks and short cut keys. Clicks ideally need to be on the pen but if the tablet has buttons some of those could be mapped to the mouse click functions. A scroll wheel of some sort needs to be on the tablet. The short cut keys I use most are shift, alt and control. It is possible to reach for the keyboard but they are better mapped to the tablet and mouse clicks in my case at least must be on the pen. This is another area to think about. On mine the top of the pen also serves as an "eraser". My pp is so crap I do use that.

Size wise I would probably go a bit smaller if I bought again and base the size around how comfortably I can control a mouse and go somewhat larger than that. Not sure how much larger but the one I have is a bit large for the desk.

John
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PS I have been off photography for a while and will be for a bit longer. I needed to look at some good photo's so popped back.