Having made a lot of tiramisu in the past, I'd say that most of my thoughts coincide with James Hoffman's findings, though before I elaborate, I will say that the best tiramisu you'll ever have isn't going to be the one people on the internet have tested; the best tiramisu is going to be the one you want to eat.
Since making that post more than nine months ago, I've slowly graduated towards the old style tiramisu's. That means no gelatin, no weird ingredients, but I do keep the addition of cream. The cream is pivotal here because unlike the video above, I simply don't have a choice of mascarpone. New Zealand mascarpone is very heavy and thick. The texture just isn't right. The addition of cream helps thin it out, and it's easier to get a nice, fluffier texture for the tiramisu cream when whipped. It's also easier to make since thick mascarpone is in my experience, quite easy to overwhip and ruin your entire batch.
On the ladyfingers, I've also had the best experience using the cheapest ones. Much like the video, I found the expensive ones to be made with the intention of being eaten instead of being a supplementary ingredient. This is fine. People like my brother buy entire packets of ladyfingers just to snack on them. Whatever. But the cheap, drier brands will reign supreme here.
In my old post, I said that I do less than two seconds for dipping. I realized I never mentioned how I dipped. In James' video, he mentioned that it's really hard to get a consistent dunk. I've never actually dunked a ladyfinger--I simply don't make enough coffee or have the right container to have a volume of liquid deep enough to dunk. Instead, I slip them into the liquid, flip them over so both sides are coated, and then take them out. The process is rather fast, and I suppose because I'm using such a shallow bowl when I'm doing it, I don't end up overdipping them.
My partner prefers it when I overdip them though. She likes the soggy coffee and alcohol soaked version where she feels like she can get drunk off it. I only take her tastes into account when I'm cooking for her and only her. She's weird and picky and likes soggy fries. 💀
For cocoa powder, I've had a really good experience using the basic baking ones. I also stopped shaving chocolate on top very early on in my tiramisu journey. In general, fluff--like shaved chocolate or how Brian Lagerstrom's video added cocoa powder into the dipping liquid--tends to eat away at the flavours you're trying to cultivate. This is not to say you shouldn't experiment! You should always fix a recipe towards what YOU want to eat. My partner likes it when I add a lot of rum, so in it goes.
On coffee, I echo James' findings that a nice medium roast will do well. I can't make espresso at home, so I tend to choose a very strong filter coffee with just a bit of variation in the flavour (meaning it doesn't just taste chocolatey or malty e.g. some fruity notes). Some people add coffee liquer into the dipping liquid to try and increase the coffee taste. I've found that it's very noticeable and people I serve it to deem it 'milky'. Give it a try if you want, but I don't think coffee liquer's for me. I have tried a light roasted coffee with fruity notes, but it tends to get weighed down by the mascarpone and cocoa powder. Also, people seem to like it when I add in a bit of instant coffee to punch darker and more bitter. The feedback has always been, "well, I expect coffee to be bitter and dark so that instant coffee does the job."
And for timing, I've only ever made the tiramisu between 8 hours to 24 hours in advance. There have been leftovers, and much like James' testing, the liquid tends to flow out. It's very noticeable when you've got a half cut slab of tiramisu; the other half of the container will have some slight pooling of liquids if you've accidentally overdipped. People do seem to like it best when I make it in the morning and then treat it to them for dinner, and there's something to be said about the slight absorption of cream into the ladyfingers and also how the coffee slowly goes into the cream itself, flavouring it, but I simply don't know enough about the process to write on it.