Logical Equivalence Check Please refer below my article which publish in Design and Reuse. https://www.design-reuse.com/articles/45547/a-guide-on-logical-equivalence-checking-flow-challenges-and-benefits.html This will give you clear understanding of what are the reason of failing LEC and ways to fix LEC with sample case study.
As we are moving towards the lower geometry from 45nm-28nm-16nm-7nm and so on, difficulties increasing in all the PPA aspects. This blogs will give you some idea about the PnR challenges and sign off challenges in lower geometry and ways to overcome those challenges.