What is the important difference between هُمْ بِمُؤْمِنِينَ and مِنْ بَعْدِ?

Sākin Mīm Rules and Ghunnah

• First has original mīm; second nūn undergoing qalb
• Both have written sākin nūn
• Both are only idghām
• Both are hamzah cases