It appears that the viral load in asymptomatic people is around the same as symptomatic people according to
one paper that looked at South Korea. I'm not sure we've conclusively figured out why some people are symptomatic while others aren't. There's been a ton of theories thrown around, including the
presence of Neanderthal DNA.
And you are absolutely correct, COVID has been significantly worse for those in the low-income bracket. Here in Salt Lake, we've seen a higher degree of infection among Hispanics and Native Americans, both of whom skew towards the lower-income bracket. There are probably several reasons this is the case, but the workplace is probably a major contributing factor. Also, the reliance on public transportation has been thrown around as another major factor as well. Access to healthcare services is a bit puzzling though. While I can certainly see the Hispanic population not having adequate access to healthcare whether due to a language barrier, lack of insurance, or just the worry about their immigration status, Native Americans have really good access and it's almost always free. I know where I work has several clinics to serve the Native population and they do a ton of outreach as well to make sure they have the services they need. Despite this, San Juan County, which has the highest Navajo population in Utah also has the highest per capita COVID rate.