SEC Alert! Commissioner Caroline A. Crenshaw: "the dominance of a handful of large market-makers internalizing orders, and conflicts of interest between market intermediaries and their customers – are even more pronounced in the options markets."
Options markets account for 65% of PFOF payments.
Fixed Income and Options: The Other Market Structures Remarks at the Fixed Income Forum Spring Roundtable: https://www.sec.gov/news/speech/crenshaw-remarks-fixed-income-forum-spring-roundtable-033023
This speech is long but worth the read. I am going to attempt to chop up the two main