Which is cool for outright speed, but there is a huge trade off.

For stenography, you consider English words as syllable sounds, learn how those sounds are represented with 1900s Stenography machine key combinations, and then to use Plover, learn where those Steno key combinations are on a normal keyboard(1).

And after that, learn the Steno shortcuts which make it fast. Standard shortcuts e.g. rolling up word endings like -ing, -ed, -end; but also personal shortcuts like "I write the phrase 'Software as a Service (SAAS)' a lot so I'll make a one-press short mapping for it". This means that everyone uses slightly different Steno combinations to say the same things - to be fast, it has to be tailored by you for the kinds of things you write.

Which boils down to relearning how to spell every word in English a second way - seems like a significant chunk of the effort towards learning a second language entirely - and also relearning how to type, in a way that will pretty much only work on your computer.

And after that, you can write English prose quickly. But it doesn't apply well to command line software. Or programming. Or foreign languages. Or tables, lists, punctuation, etc. because you aren't typing character by character anymore. Things like 'find ./ -mtime -3 | grep mp3 | vim -' or 'vim XF86Config' - making sure to get the capitals right - have no easy English spoken representation, so until and unless you make a Stenographic form for it for yourself you will have to switch Plover off and type normally.

Mirabai Knight (the linked video presenter) suggests adding combinations for common programming patterns, essentially using it like a code-snippets engine. I don't know if this works well or not.

Another problem is right at the first bit where you need to "consider English words as sounds" you find that English has different words which sound the same (bear/bare, their/there/they're for example). So you can't just press the keys for how the word sounds, you also have to dodge around the words where that doesn't work, and remember the alternate mappings which only apply to certain words. That means you can't just learn a new word and type it because it might not have an obvious Steno representation, it might have one that's dodged around another word or is shortened beyond what you'd expect just from the syllable sounds.

Fundamentally this happens because some of the information in reading English is carried by the context. You hear "the bear mauled the victim" and you know which word is meant. Historically Stenography was encoding the syllable sounds directly to paper, and then the stenographer would read them back - it didn't matter that different words encoded the same way as the stenographer could interpret the context when reading back in the same way as they could when hearing the sentence in the first place. So Stenography was a fast way to take dictation, but producing a written transcript or document meant going over everything a second time reading it back and transcribing it - twice the effort or more, and not usually discussed when talking about speed.

Plover, however, is avoiding that work by automatically expanding the key combinations out to full words, saving you the rereading and rewriting work. At this point it does matter if separate words encode the same way because it can't choose one from the context like you can. So you have to interpret the context and deliberately encode the words as if they sounded different to give an unambiguous feed to Plover.

I can't help but wonder if you could get 25% of the benefit with 3% of the effort by 1. writing less (he says, after writing 700 words about it), 2. setting up some AutoHotkey style keyboard shortcuts for phrases you write a lot, and 3. having as many templated email messages as you can get away with.

(1). You can't use a normal keyboard, you need one which can handle 10-12 concurrent keypresses (aka anti-ghosting / n-key rollover). Most keyboards and laptops top out at ~6 simultaneous keypresses registering properly. Plover is why I have a Microsoft SideWinder X4 which is one of the few that can handle any amount).