Hii!
Actually NEST exam tests the logical ability of a candidate as this field is mainly related to research and thus, creative, critical and logical thinking is very important. Therefore the questions come in a twisted format and you need to reach to a conclusion accordingly. You can't quite compare JEE Mains and NEST because they represent different career fields and so the questions are oriented accordingly.
In order to prepare for NEST, try and get the previous year question papers as much as possible and solve them. You will get an idea of the question. NEST official website also provides sample papers and mock tests, you can login and attempt them.
The link given below will help you with more information -

https://university.careers360.com/articles/nest-exam-pattern/amp

Hope this helps.
Good luck!