Between the S and the CT I think it's 50/50 on who will be delivering to 'real' customers (Rivian not delivering to employees, and Tesla not delivering Austin cars to ???). It's exciting... and while there is probably some overlap in R1S/R1T and CT customers, the real threat should be felt by the ICE manufactures.
One of the 'reasons' Rivian is going to fail from the video above is that it's manufacturing is growing too fast and isn't Tesla (whatever that means), inferring it wasn't agile (when you are provisioning to scale to 1M+ year, not sure how much agility is actually required). Yet, they made two R1S, and it is supposed to be 85% common with the R1T, so the ability to flex/adopt the line must be fairly robust? Also, I saw a pic with a seemingly random set of colors in the manufacturing process, so maybe they aren't as color batch constrained as Tesla? To be fair, it wasn't known from the picture if the colors were painted in the same order as they were shown in the picture (think they were 'drying'), so maybe they are also constrained by batch paint jobs.