AM62P: What difference of between AM62P and AM62B?

These are different device families (AM62 and AM62P) 

AM62P: https://www.ti.com/product/AM62P

AM62: https://www.ti.com/product/AM625  

You can look at the datasheet block diagrams to understand the differences as well as look at the part numbers within each device family. 

AM62B is essentially some time used for the EVM , where the original EVM was SK-AM62 and the newer EVM is either SK-AM62B or SK-AM62B-P1 ( latest and recommended). B denotes the these EVMs have HSFS devices on them. 

Let us know if you have more questions