Confused to use join or sub-query SQL?
but which is more accurate / relevant for more number of records ?


Neither and both. The optimizer is free to rewrite subqueries as joins. 

For clarity, since you don't need any columns from Table2, I'd go with a third option and use EXISTS. 

This is only a benefit for the reader in this case. In other cases, writing a join may result in unwanted row duplication, which will typically lead someone to add a DISTINCT or GROUP BY to remove them, which are unnecessary with EXISTS or IN...

Of course, it's different with NOT IN. If NULLs exist in the relation, you'll get an empty result set. This can be quite confusing to beginning query writers.

As a style choice, I go with EXISTS or NOT EXISTS when I'm referencing a subquery, and IN/NOT IN when I have a list of literal values.

Hope this helps!