Reporting back! Thanks Wurg and TCMS.
So I messed around a little bit with UnRen v0.7 and UnRen v0.6. Sure enough, for me, I had much more success with v0.6 of UnRen. I don't know if this feedback helps with the future development of UnRen as I could not zero in why I ran across some issues, but here's my observations nonetheless (of what I recalled anyway).
For both versions, I did not use any other options other than the first two which were extracting RPAs and decompiling files. I am using the 64-bit version of Win10 and used "Kingdom of Deception" of Hreinn Games for most of the testing. Other than normal OS processes, no other programs were running besides an internet browser.
While using v0.7 of UnRen, it was able to successfully extract most of the files within RPAs. A few files came out "dead". To root out if I had a corrupted archive to begin with, I made sure to get fresh downloads directly from the developers' links. As far as I am able to tell, these weren't Ren'Py v7 games so the known issue with layering should not be affecting anything. In addition, UnRen v0.7 either could not locate files to decompile (which happened most frequently) or just garbled it up when it did find files. I can only surmise that something is going sideways with its new feature of being able to decompile things within itself. Also notably, the last time I tried to use UnRen v0.7 (and the only time this occurred), Windows Defender at first stopped UnRen from running and then asked if I wished to continue. I don't know if that last bit is relevant to anything or not.
I ran into none of these issues while using UnRen v0.6 provided by Wurg in the post above. UnRen v0.6 was able to extract RPA files, and was able to locate and decompile rpyc files without any problems--just as I remembered.
Again, this is a wonderful tool and I hope this bit of feedback regarding UnRen v0.7 helps to make it better. Okay, I'm off to play my first game on this new laptop! Woo~!