Option D: dont attend any university and just get to work. The value of university degrees, even purely for signalling, are at an all-time low and descending. For learning, you can do free online video courses. 

There are highly valuable tasks AI researchers dont do because they are low status / boring / hard to fund. You could get started on them independently. 

You'd need a mentor at some point to avoid wasting time on irrevelant things / to hold you accountable.

I think if you are highly self-motivated, independent, and creative, this could be the best option by an order of magnitude. 

Intuitively, I think 3 > 1 > 2. Mentor quality differs between institutions; as does learning speed; as does the network you leave with (i.e. your classmates and mentors). 

If you are psychologically able to put in the work for a good GPA at the good school, that seems like an excellent thing to do. If you find out that it's not psychologically sustainable for you to do, you can adjust your plans accordingly. It's not obvious to me that you are currently able to assess your GPA correctly - maybe you significantly over- or underestimate what results you will end up with.

However, according to some EAs, chasing a high GPA is mostly for signaling rather than improving my research abilities, because some college courses are irrelevant to AI risks.(I'm uncretain about this view)

I'd personally strongly disagree with this. I think a core problem of some EA work is that it keeps reinventing the wheel; that it overlooks important existing literatures; and that it struggles to illustrate its relevance to existing fields (and thus is not picked up or well regarded by researchers). A decent university education in the field you wanna engage in will be helpful even if it includes courses that do not currently seem directly AI research related - it may help you gain the ability to understand and persuade future colleagues in the field, for example.
 

My hunch is it doesn't matter. Master programs, especially in policy, tend to be cash cows. That's not to say they're worthless. But you are paying money for the network, credential, and access to a cool career. So admission standards are lower. It wouldn't surprise me if some internationally recognized exam like GRE took outsized weight in admissions.

When it does matter, it's not obvious to me that (1) is worst. The more prestigious Master's programs (typically those with full funding) do try to train their admissions staff to recognize differences in preparation across schools. And I wouldn't discount peer effects or building general cognitive endurance through a challenging curriculum.

Finally, I really don't know what middle-tier and top-tier mean here. And I think you should try to find a few people who took some Taiwan -> US master's transition to get their sense of where the ranking falls / how much it matters.  I'm familiar with "tiers" in a few contexts: (1) NYC high schools, (2) US college admissions, and (3) Econ PhD admissions.  There's no portable rule that works for all cases. Sometimes, the quality difference drops really sharply at some rank. Other times, the quality difference is flat through the distribution. Other times, the real quality distinction is within-a-school rather than across schools (e.g. the prestige at a school comes from a specific program than only half the applicants get accepted into)

comment rather than answer cuz its a different discussion: in some cases a high GPA is a red flag cuz it means a person could've taken harder classes and didn't^[1]. In the US, high schools adjust for this by making an A in an AP worth 5 out of 4, but i haven't caught wind of solutions like that in college.

1. ^{^}

   plus there's enough grade inflation out there that isn't normalized across institutions or even within institutions.