TEMPDB File Growth with Multiple Files
Answer to your question will depend on the answer to the following.

Most queries need 75% meaning 75MB in your case. 


Do you mean all queries combined need 75MB?
Each of those queries need 75MB individually?


If all queries combined need 75MB then you can have multiple smaller files and you will not increase overall space because those files should not grow.

If each query needs 75MB then are they running in parallel or serial? If parallel you must be using more than 100MB today.  If serial than I do not see why you need multiple tempDB files.  

Are you seeing contention on PFS and SGAM pages?  

I suggest you review these articles regarding your question.


https://www.sqlskills.com/blogs/paul/the-accidental-dba-day-27-of-30-troubleshooting-tempdb-contention/
https://support.microsoft.com/en-us/help/2154845/recommendations-to-reduce-allocation-contention-in-sql-server-tempdb-d