Yes.  The space within the data file for that database will be reused by that database to hold ne data without growing... provided that you've actually deleted whole pages OR...

STRING_AGG (Transact-SQL)

• ‎04‎/‎18‎/‎2017 

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It's not available in SQL Server...

I don't know why what you said happened actually happened but I'd take it as a lesson learned and have two different partition schemes.  I've not run into the problem...

Here's an example post of what a "tuning series" might actually start with.
https://www.sqlservercentral.com/Forums/1983195/Adding-Indexes-to-Tables

No... not volunteering... I still have way too much on my plate as...

IF that's the case and understanding that

Step 2 is to realize that you can't use GO in a variable that you're going to execute.

Yes.  Start at the following article.
http://www.sqlservercentral.com/articles/Crosstab/65048/

If you'd like some more detailed help at the code level, then please see the article at the first link...