Yes APM is the capitated payment model that CMS has proposed to roll out on 1/1/20 that will impact 40% of RO practices.
HOPPS changes in 2020 for RO have been discussed in other threads but include loosening of supervision requirements and acceleration of site-neturality (see here:
6 takeaways for cancer programs from the 2020 HOPPS Proposed Rule)
MPFS is the 2020 Medicare fee for service rates which are essentially unchanged from 2019.