Shi Guwen is a kind of seal script, but seal script is very common as a seal font. If you want to learn calligraphy, you can consider going to Shi Guwen.
However, the art of calligraphy, I think many later calligraphers are better, so there is no need to visit things like Shi Guwen and Jinwen. Wang Youjun, Yan Zhenqing, Liu Gongquan, and even the weeds Zhang Xu and Huai Su are much better than the words carved on stone and metal. Shi Guwen and Jin Wen, as characters, have important research significance. But as calligraphy, I don't think it can be compared with real brush calligraphy. After all, the emergence of calligraphy is due to the writing brush.
As for which is earlier, the cauldron belongs to the Zhou Dynasty, and bronze inscriptions are also used. Shi Guwen belongs to the pre-Qin period, which is close to Da Zhuan. Of course, the cauldron was earlier.