I said it before, but I really agree with you here so I'm gonna reply and agree again; in Bloodletters, the players know the system. Maybe not all 100%, but they all have a working knowledge of it. For people whose problem with Rollplay:Blades is the time it takes to choose/position/resolve/question everything and say "Well, it's clearly the system then, right?"... go watch the more recent Bloodletters games. When the game doesn't have to be explained/re-explained constantly, the flow is far more on point, and the rolling-forward action and drama follows right along nicely.
Rollplay:Blades really could use having at least one Stras. I mean, maybe not actually Stras, but somebody in the crew who has a level of system mastery where they can help the other players out from that side of the table. Think of the progress that Dan has made on CoS, where he's really bought into D&D, he put the time in and learned the system and the mechanics, including the ones that may not directly apply to his current character/class. They have him constantly there as the player who is engaged and informed on a mechanical level, and it helps them out drastically with keeping things moving.
A possible two-sided coin here as well is the player number. In my experience watching, playing, and running Blades, I really think that 3 players > 4 players. Passing spotlight time and letting each player stretch out and be awesome when their time to shine hits without stepping on other players' toes or having one or more players sidelined for long stretches seems to flow better with 3. That's just personal experience/observation, your mileage may vary etc. It's maybe a little less apparent on non-streamed/camera games where you don't have that sidelined player still there being watched as they wait/quip/browse Reddit/whatever, but on stream it is easily apparent.
Now, the other side of the coin however is also not to be discounted for this scenario specifically: each player, being a streamer in their own right, brings some of their own audience in with them from outside of Rollplay potentially. And fewer players does indeed mean a smaller pool of "extra" viewers coming in. So, that's not a concrete plus/minus.