Drawing tablet 100%. Not only will drawing with a mouse produce worse results, it is also very hard on your wrists.
Personally, I use a wacom Intuos with krita software for drawing. As far as I could delve, Wacom makes the best graphics tablets, but are usually more expensive.
I found a really good deal on one though, so I snagged it. Immediately after I purchased it, my art got better. Pressure controlled width, and opacity are amazeballs.
If you need one:
https://pctechtest.com/best-wacom-drawing-tablets
