I suspect high skill immigration directly helps probably with other risks more than with AI due to the potential ease of espionage with software (though some huge data sets are impractical to steal). However, as risks from AI are likely more immanent, most of the net benefit will likely be concentrated with reductions in risk there, provided such changes are done carefully.
As for brain drain, it seems to be a net economic benefit to both sides, even if one side gets further ahead in the strategic sense: https://en.wikipedia.org/wiki/Human_capital_flight
Basically, smart people go places where they earn more, and send back larger remitances. Some plausibly good effect on home country institutions too: https://en.wikipedia.org/wiki/Human_capital_flight#Democracy,_human_rights_and_liberal_values
We have lived in a multi-polar world where human alignment is a critical key to power: therefore in the most competitive systems, some humans got a lot of what they wanted. In the future with better AI, humans won't be doing as much of the problem solving, so keeping humans happy, motivating them, etc. might become less relevant to keeping strategic advantage. Why Nations Fail has a lot of examples on this sort of idea.
It's also true that states aren't unified rational actors, so this sort of analysis is more of a course grained description of what happens over time: in the long run, the most competitive systems win, but in the short run smaller coalition dynamics might prevent larger states from exploiting their position of advantage to the maximal degree.
As for happiness, autonomy doesn't require having all options, just some options. The US is simultaneously very strong, while also having lots of autonomy for its citizens. The US was less likely to respect the autonomy of other countries during the cold war when it percieved existential risks from Communism: centralized power can be compatible with increased autonomy, but you want the centralized power to be in a system which is less likely to abuse power (though all systems abuse power to some degree).
The most up to date version of this post can be found here: https://theconsequentialist.wordpress.com/2017/12/05/strategic-high-skill-immigration/
At times the signal house was densely populated and a bunch of people got sick. These problems went away over time as some moved out, and we standardized better health practices (hand sanitizer freely available, people spreading out or working from their rooms if sick, etc).
I think it is better to assess personal fit for the bootcamp. There are a lot of advantages I think you can get from the program that would be difficult to acquire quickly on your own.
Aside from lectures, a lot of the program was self study, including a lot of my most productive time at the bootcamp, but there
was normally the option to get help, and it was this help, advice, and strategy that I think made the program far more productive than what I would have done on my own, or in another bootcamp for that matter (I am under the impression longer bootcamps may develop specific skills at using the software better, but they don't convey nearly the same level of conceptual understanding of statistics in data science, and likewise there are many types of mistakes graduates of other programs will make that graduates of Signal's cohort have been taught not to). When there was not the option to get help, I usually shifted my work schedule and it wasn't much of a problem: there are so many projects to work on, that there was almost always something productive to work on where I wouldn't get stuck (optional exercises on prior projects or making prior projects better). I can see this being very frustrating for some people though, as getting stuck and not having immediate feedback interrupts flow.
Many of the organizational problems didn't seem to really be problems, and seemed more like differences which are good for some and not for others. Pair programming was not always optimal due to the large degree of differences between students. It wouldn't have made sense for everyone to pair program since it would have been holding back some of the faster students. A more rigid structure would have helped people who were less naturally self directed/focused though. Organizational problems that happened with respect to the first cohort in terms of setting up (furniture, internet, whiteboards, etc.) are unlikely to be problems for future cohorts now that the instructors have learned from experience and have a place set up. The first cohort took the risks and costs of such things, which later cohorts probably won't have to worry about.
This is not like other bootcamps, it is less expensive, more individually focused rather than having the entire group doing all the same curriculum, and there are a bunch of rationalists iteratively helping you decide which jobs are best to apply to, who can network you into what position, and which skills actually matter most for aiming for the specific jobs you are aimed at. I don't expect you to be able to have the same opportunities at a normal bootcamp, but a normal bootcamp is probably also lower risk if you don't trust yourself to make things work out (other programs may have quizzes where they throw you out if you fail, and essentially force you to remain focused, with Signal you are more in control yourself, and can take time off to apply to jobs.