Well, the guy who fixed my phone from a bootloop and bricked state said he has done the s-off, found a suitable stock RUU and installed, then he put S-ON back and unlocked bootloader if I decide to do any mods in the future.
1- If you are 100% stock then Settings -> About should also show your correct version number
2- you rooted the phone, so that
may or
may not have changed some system files, so OTA may not work
3- once S-Off stay S-Off, my
personal opinion
In my humble opinion, three choices really, when it comes to "modding" or not your phone:
A) stay stock and don't mess with it to get OTAs
B) you cannot achieve S-OFF (due to newer hboots, or device problems) -> fine live with an unlocked bootloader, and accept the fact that you cannot install OTAs .... you can however "download and install later" the OTA, then pull it to your phone, and use the signed firmware.zip in it
C) you can achieve S-OFF and want to mod your phone -> then do it, get S-Off and enjoy the freedom (but don't flash things not meant for your phone!! this goes for S-On too)
Of course you're going to say that "but S-Off is dangerous", it's a double edged sword... sometimes you are able save your phone thanks to S-Off, and sometimes you can brick it completely.
But then again, you can easily brick an S-On phone too (especially one that is modded), and much more difficult to save than an S-Off phone.
^^ All that is my personal opinion, and I'm not suggesting you S-Off, but if you want to mod your phone (whether S-On or S-Off), you need to be aware of what may, or may not, go wrong, and have done some reading and research
Good Luck