My understanding probably is too naive. It depends on how confident you feel
with your research capability and how good your research areas are. If you
are confident, take the position in the tie 3 university. In the next few
years, you may get your grants awarded and your papers published. Then move
back to tie 2 or 1. I know many friends graduating from top 10 universities
have been in the postdoc positions over three or even more than 5 years. I
am currently working in a tie 2 university. Many years ago, I felt regretted
to take this position. Today, I feel that I made a great decision.