Will you be using it mostly in Lightroom, or also in Photoshop?
There’s a kind of continuum of uses for a tablet:
- Advanced compositing, digital painting/drawing with simulated pencils and brushes
- Painting masks for photos, for retouching or compositing — many Lightroom users fall in this category
- Simple mouse replacement for general computer use
Generally, the higher up you are in that list, the more money you want to spend.
A simple mouse replacement tablet can be small and have basic features, where you spend under $200.
For photographic masking and basic retouching, it helps to have a small to medium sized tablet and a stylus with good pressure sensitivity, usually in the $150–500 range. If the tablet is mostly for use in Lightroom, this type of tablet would be typical. I use a small Wacom Intuos Pro.
If you want to make digital paintings, draw digital comic books, or do advanced compositing in Photoshop with custom brushes, especially the brushes that respond to things like the angle you hold the stylus and if you are turning the stylus as you paint, you’ll definitely be using a Wacom Intuos Pro. For those users, the medium to large sizes can be preferable for drawing/painting at the same size as on paper.
If, on top of all that, you’d like to paint/draw on a document being shown on the tablet itself because the tablet has a display in it, then you want to pay even more for a Wacom Cintiq Pen Display.
Another low-end/high-end differentiator is that the more expensive models have more programmable buttons (ExpressKeys), and may have a Touch Ring. I mapped my Touch Ring so that I can spin it to change values in Lightroom Classic options. In Adobe Premiere Pro I programmed the Touch Ring to be a jog/shuttle wheel for the video timeline.
The short version:
Photographers can get away with small/basic tablets.
Digital fine art painters/sketchers can make use of the features in the higher end tablets.