If Omicron has higher reinfection risk this is relevant to any apparent transmissibility advantages over Delta. South Africa has a very low vaccination rate, yet had high population immunity against the coronavirus due to prior infection immunity. In such a population, Delta reinfection would be low.
Omicron has a number of mutations that are associated with higher transmissibility, but the visible overall transmission advantage may also be in part due to immune evasion advantage.
Likewise there are early reports about potentially milder disease with fewer symptoms of loss of smell. But these are based on cases primarily in younger people without comorbidities who would normally have milder symptoms. Keep in mind Delta itself was associated with different more common cold like symptoms than Alpha and the wild type, but did not end up having milder disease.
With more data we will be able to answer both questions. For now we should just be cautious about the early data. Anecdotal case reports and limited epidemiological data don't substitute for more comprehensive immunological lab data.
Early reports suggest that omicron causes mild symptoms...I don't remember delta symptoms being described as mild. I think the knee-jerk travel restrictions may be excessive and they don't even make sense. We're banning African countries in which the variant has yet to be seen, and we're not banning European countries in which the presence of the variant has been confirmed.
We don't seem to be learning how to better respond to new developments.