Can all kinds of calligraphy fonts be practiced with a pen?

Yes, but the effect of writing with a pen and a brush is different. No matter which font can be written with tools, the form of presentation is different. If you practice with a pen, you are practicing pen calligraphy. No problem. As I said upstairs, Oracle Bone Inscriptions is also engraved, but we can evolve into a style of writing, and both brushes and pens can write. In addition, hard pen calligraphy mainly uses pens. But not limited to pens. Hard pen is relative to writing brush. Now all kinds of calligraphy pens can write very good results. But the pens used in pen calligraphy are ordinary pens, excluding those "improved" calligraphy pens. If you practice Chinese characters, you'd better use an ordinary pen, which is simple and practical. A pen is just a tool. You can change to other writing tools. This is just a process of getting familiar with writing tools.