- Timewarp was a cia file of the DS whitelist before it was updated. This is the file was used to block DS flashcards that originally worked on the 3ds, but it would install the old whitelist before it blocked said cards.
(there was also a one people called the "browser timewarp" cia, but you likely mean the ds whitelist)
- NVRAM was the next level up for the DS profile entrypoint, it would "install" the entrypoint permanently if you did it right. So you could play ds games and it wouldn't reset the ds profile settings like it usually does.
- And MSET was the profile exploit, but it was for New3DS system. It was an older version of the system settings (which is what MSET is I believe) that you usually wouldn't get on the n3ds systems.
I'm just going off memory so forgive me if that isn't all correct, but that's my understanding of these things as I can recall it.
It's a surprising coincidence to here of someone with my exact same situation (since now there's a whole bunch of options for hax). I imported my n3ds from Australia as it uses the European region, and at the time, they were the only known English consoles to have 9.0 firmware out of the box. Having a gateway from day 1, I knew I had to have it available for my new system as I was giving away my original one after upgrading. And you listed almost the exact same stages for changing your system as I did.
Oh and just make sure you leave your gateway well alone whilst you upgrade to b9s. I know gateway has it's own version, but I believe that's still only a9lh (the best, before b9s) and it also locks you into gateway's shit and basically screws your console. (you can use certain ds flashcards with ntrboothax to hack any firmware now, but it'll be easier to just avoid gw for the moment, at least on sysnand)
So don't try doing any gateway stuff while you're updating to b9s, and also don't try using it in sysnand either.
I'm no pro especially on how gateway should be used with current firmware, but I do know that at one point I stopped using mine and it was due to the scares about gateway actually removing hax because their version of a9lh doesn''t have write protection or something (which the one in the 3ds guide does).
This thread seems to have all the info regarding that sort of thing (
https://gbatemp.net/threads/tutorial-using-luma3ds-gateway-on-b9s.431691/), So I'd say go there after you update to b9s and before using your gateway or any of it's files. I only used my gw toward the end for the cheat engine, I might check it out again though and see about running it in an emunand after I get a bit more up to speed on the do's and don't concerning gateway and b9s, cos they might have changed since the last time I was a heavy gw user.