There are a different number of mechakoopas and Bowser has a different health value in the different difficulties on Frightmare, the different difficulties are more there for consistency sake with the other categories.

Hey MP5 fam, just so you know in light of the most recent Frightmare Hard run by lunk, I've decided to add an milliseconds section when submitting runs. His time was very close to the WR so I think it is now fair to have milliseconds when shooting for that WR time. Good luck and have fun!

¤Edit¤ If you would like to re-time your run (just for the sake of having the milliseconds on the leaderboard, I did personally) feel free to resubmit runs

Oh shit yeah, just checked that. It's been a while since I touched the game, however the same principle applies to making the speedrun longer for essentially no reason.

Correct, Frightmare only goes up to Hard difficulty. Also, changing the difficulty for story mode just makes the run longer by giving the Koopa Kids more coins to start in each dream; essentially it makes the run longer arbitrarily. And the Intense difficulty just does the same thing, it's just more of a NG+ kind of situation because it only becomes available after completing the story on hard mode. However I can add that as a misc. category if you would like. Let me know if you have any more questions!

Absolutely man I look forward to it

Everyone makes good points here and (I'm assuming) that Almo saw that I claimed to be the WR holder for BP only. And I recognize that this is a meme/challenge category and whether it is recognized on the speedrun.com leaderboards or not I can be happy and proud with what I did. And it is true, I was too intimidated to run any% or 100% to start because I don't know any of the glitches; so I thought of something to kind of ease in to it you know? It wasn't serious, I wasn't exactly trying to be necessarily competitive for it, regardless I had fun with it. I don't think there needs to be a misc. category for it on the leaderboards either, I can just discuss it with other runners or people that want to run it. I made a post earlier this week and I was told by Zephiles that this leaderboard is used for main categories. So honestly I think that just having the 3 main categories (for now at least) is totally okay and that we should just stop trying to invent new "main categories".

At least that's my 2 cents