Hey there

They are quite similar but it is seen that students attempt more question and get more marks in actual exam than abhyas or test series. NTA designs the Abhyas test series to teach students how to give online test and manage time during exam. so it is beneficial to take the mocks of NTA. In addition to it join a test series too and practice to increase speed see mistakes to score more during actual exams.

check the link

https://learn.careers360.com/test-series-jee-main-april/

good luck

Dear,

Level of the paper is almost moderate. Actual paper can be tougher as well as easier. But I would suggest you to give paper with full attention and preparation. It will increase your practise as well as confidence. Analyze the paper and see your mistakes. Also don't be overconfident on high score, check the scope to increase marks.There were also few previous years questions  in all the tests as well as all the sections that is physics, Chemistry and maths so that student gets the idea of type of concepts asked in actual exam.

Hope this helps!