Yo! Heard you comment on some wolf lineart pic. I'll give ya some advice on digital art!
Using a graphics or art tablet with a stabilizer (or correction depending on what software you use) on about 10-19 will help you get really really smooth lines.
A graphics tablet will also help you get pen pressure, which is how dark and big the lines are depending on how hard you press. This mimics a real pen or pencil. Tablets also have a glossy paper-like surface, which can help you since you seem like you do traditional art a lot!
I'd recommend tablets from Huion, and Wacom. You should probably get the Huion 1060+ or the Huion h610. The h610 is what I use.
Wacom should most likely be a Wacom Bamboo or a Wacom Intous, like the Intous Draw or Intous Art. They're about 80 and 120 dollars.
Softwares might be FireAlpaca, Medibang, Gimp, Krita, or SAI. SAI costs money though. I've only had experience with FireAlpaca and Medibang however.
Hope this helped an artist in need of advice! ^^