> 3) OpenBSD adds pledge/unveil system calls from the browser, to prevent it from reading/writing files where it should not (plus I browse under a different user than I do other things with high confidence there will not be a privilege escalation; also they say the pledge/unveil support is easier to implement in Chrome/Iridium than in Firefox because of the cleaner separations of concerns in the code organization (my wording; though they have probably also put pledge/unveil in FF also for all I know),

Just FTR, Firefox is adding pledge/unveil support for OpenBSD in version 72, see https://marc.info/?l=openbsd-ports&m=157325338020502&w=2