Is this good writing style '成了有所成就的成功者。'?
还有一些人，学历较低，智商也不出众，但却成了有所成就的成功者。

This part says:
成了有所成就的成功者。 'become somewhat successful succeeders'

In English that would not really be acceptable. Does it seem strange to Chinese ears or just completely normal?

Question

Is this good writing style '成了有所成就的成功者。'?
还有一些人，学历较低，智商也不出众，但却成了有所成就的成功者。

This part says:
成了有所成就的成功者。 'become somewhat successful succeeders'

In English that would not really be acceptable. Does it seem strange to Chinese ears or just completely normal?

Answer

To me I can't say it's grammatically wrong, but this is not how I would say it, cuz 有所成就 and 成功者 are basically talking about the same thing so it sounds repetitive (as it did in its english translation). So simply 有所成就的人would suffice.

Answer

It's another sloppy language.
Strictly speaking, I would say it's wrong. Because this sentence has a problem which is called "semantic repetition".  "有所成就的“和 ”成功“ are repeated. It shall be changed into " 成了有所成就的人” or" 成了(一个)成功者“

Answer

It's grammatically correct, but ounds a little strange. Usually we would say "取得了一定的成就" or "小有成就"

Answer

your sentence is ok, I would simply say 但却有所成就。we chinese normally cut it short.

Answer

It is correct to Chinese