if I use the codes in/from the excel spreadsheet, can’t I just copy and paste into PEP?
Sure, if you are happy with that, fine.
Isn’t IRScrutinizer for code generation? Into HEX? (I never used it)
It can do that and much more. You can import a bunch of interesting commands, and generate a Pronto file containing those with a few key clicks. That file can then be imported into PEP.