first
It's too early for a four-year-old to practice hard pen or soft pen! If you want to learn China's calligraphy, start at the age of five. If you want to learn hard pen calligraphy, it's not too late to practice in primary school. Practicing too early is likely to backfire.
then
There are men and women in the font. If you want to learn China's calligraphy well, you should start with regular script, and you can use European style, Yan style and Liu Ti.
finally
If you want to write well, I suggest learning China's calligraphy. Kill two birds with one stone, even a hard pen can write well.
Then ask (unknown) teachers for guidance. If you want to write well, you must have a teacher to teach!