Practicing regular script can help you understand the structure, strokes and strength of Chinese characters, and can also train patience.
And even at work, I can spare half an hour to an hour to write during my lunch break every day, but I don't need to practice for several years unless I have an exam. If you pay general attention, you can get started in about three months.
When practicing, it is recommended to practice only one person's handwriting, because different people's handwriting feels different, and they will hesitate when thinking together. I practiced Ou Yangxun's regular script and running script. The two you chose are both famous modern calligraphers, so you can choose either one.
You don't need to practice running script unless you want to practice running script instead of running script in the end.
Practice regular script before practicing running script. In fact, after you have laid a good foundation, you will find that the speed of practice is much faster than before, and you have a chapter structure instead of scribbling. There were many famous running scripts in the Song Dynasty. Although the regular script in the Tang Dynasty was good, everyone's running script was also very beautiful.
If you choose a modern copybook, you should pay attention to whether the font has structure, whether the strokes are smooth, and whether you choose clear handwriting instead of cursive script. After all, your handwriting should be read clearly.