All Covid-19 variants have a lipid envelope, all Covid-19 variants bind to the ACE-2 receptor. After binding Omicron is preferential to endosomal encapsulation while other variants aren't. The other variants use TMPRSS2 in the cell to achieve cell fusion and TMPRSS2 can be heavily expressed in the lungs although not in the upper respiratory system but yes Omicron can infect the lungs just not as effectively.

They think Omicron is half as severe as Delta but Delta is twice as severe as the original Covid-19 which would put Omicron on par with the original Covid-19. What you would see in Omicron is a lower ICU rate per capita than Delta and probably lower than the original Covid-19 offset a bit by the higher transmissibility. I would think intubations in Omicron would be low but comorbidities and a weakened immune system would mean a greater chance of higher lung infectivity. But then you still have Delta infections in the mix.