Shall I pursue either B.Tech or integrated MSc to become an atomic scientist?

integrated m.sc is better option

go integrated msc.......

It doesn't matter but one really wants to become an atomic scientist, Integrated Msc would be more beneficial.

Prepare for Tata Institute or any other prestigious like BITS.

The field of science and becoming a scientist itself demands rigorous research and energy and time investment. Therefore a course of such kind of study,research work etc should be sought for to become an Atomic scientist.Hence opting for Integrated Msc should be given preference as it will help you