Ive known Aries Sun alphas.
Ive seen a Taurus Sun alpha, although having a unique and loud personality is not necessarily alpha.
Ive known a Gemini Sun alpha, in both male and female, both had a lot of Scorpio too, which I think is one of the more common alpha signs.
Ive known a Cancer Sun alpha before, although I don't think its that common.
Ive known plenty Leo Sun alphas.
Ive never met a Virgo Sun alpha or someone known to have Virgo in their chart, so agree with that being beta.
Ive not known any Sagittarius Sun alphas but plenty Sag Mars alphas.
Ive not really known a Capricorn alphas.
Ive known a really cool Aquarius Sun alpha. They had a Leo Moon conjunct Jupiter.
Ive not known any Pisces Sun alphas.
That's my list of known alphas which I tried to keep to Sun signs unless other placements were known. There will be variables in making an un alpha Sun into an alpha by having a strong Mars, like in the Libra Sun Sag Mars example, so the Libra Sun example doesn't work. So the list wont work. Oh well.