I feel like Seaside First could also be faster if some coins gotten in Sand or something were to be routed out. The only problem with this is that the coins aren't exactly out of the way enough to justify taking them out.

I've had that happen in one of my runs (I think my PB does that). It's not faster in any respect, but it's not lethal either. :P

Several months ago, I was running using cup resets as opposed to A spamming (I've done the ladder since returning to the category a couple of weeks ago). I use and Old 3DS XL with cartridge, and in my experience, it saves a little under 1 minute and 30 seconds in total, contrary to MKWilliam's claim. With that being said, I'm not exactly sure console difference has that much of an effect on loading times, seeing as, with A spamming, you have to deal with 64 loading screens (one after selecting "Next Race" and another after skipping through the course introduction). Therefore, even if the difference of loading times were a mere one second between Old and New 3DS, I would be losing over a minute to a New 3DS user (which I'm pretty sure isn't the case, seeing as the WR holders for both the glitch and no-glitch categories use old 3DS's). I doubt this would be any different with cup resets.

They use the Metal Mario combo simply because it's the fastest. I personally used Luigi in one of my runs to buff up my acceleration a bit to be able to recover from hits. I only found this useful in one case, not that much at that.