What are recommended ways\tools for processing large data from Excel Files?
pandas loads a csv upto 10x faster than excel. So, if you can, please convert these files to csv, which ever ones that are being loaded several times.

I have been using cython, which seems to speedup read functions and processing. Please follow this link for more details. It says, that using cython speeds up the processing 10x.

Suggestion: If you can, I would recommend to store data in database and use an orm like django/peewee for the data processing. 

Please lemme know if you have any other queries.