Thanks for the input
@Ibuprophen and
@bilgerryan! So for the sake of confirmation I tested it out. I was able to flash OF1 using Odin3 v3.10.7, and then re-download PL1 from the OTA notification. The notification popped up less than a minute after starting my phone. I installed it and verified I had PL1 again.
They also had the I545VRSGPL1 firmware over at Sammobile, so I decided to test it out as well. I flashed back to OF1 using Odin, and then back to PL1, and then back to OF1 again. So I seem to be able to freely move between the two firmwares.
However, I am a little confused. I assumed that flashing these firmwares would be like performing a factory reset (except for the OTA update, which I knew wouldn't clear my data), but it didn't seem to work that way. I did do a factory reset before doing any flashing, but after the first flash I connected one Google account and also connected to WiFi. It never seemed to reset my phone. I never had to go through activation, and the phone retained the WiFi connection and Google account. Am I right in thinking I was flashing the stock ROMs? I did go into about phone and check the baseband version every time, and even kept notes:
Starting Firmware: Baseband I545VRSGPL1 [I did a factory reset before flashing any firmware]
After First Odin Flash: Baseband I545VRUGOF1 [I connected the phone to WiFi and added a Google Account]
After OTA Flash: Baseband I545VRSGPL1 [Still connected to WiFi and Google account]
After Second Odin Flash: Baseband I545VRUGOF1 [Still connected to WiFi and Google account]
After Third Odin Flash: Baseband I545VRSGPL1 [Still connected to WiFi and Google account]
After Fourth Odin Flash: Baseband I545VRUGOF1 [Still connected to WiFi and Google account]
If my phone isn't being completely reset, does that mean these methods would not work to unbrick my phone if it were to get soft-brick?