Let's remember that some Vulcan characters seem to miss out on pon farr, either explicitly or implicitly (Tuvok vs. the crews of the fully Vulcan-crewed ships). And then let's recall that the chaste 1960s episode "Amok Time" defined pon farr not as the urge to mate, as in madly copulate, but as the urge to
find a mate, as in get married. Indeed, apart from that ST3 thing, all known occurrences of pon farr have been resolved without copulation!
It might well be that pon farr is a bachelor-only thing, explaining why it's so extremely unlikely to occur on screen despite Vulcanoid-heavy settings or storylines. When the couple is formed, there's no further mating urge.
This would jibe with Spock's second puberty, too: one time with Saavik was enough, even though Spock clearly matured several seven-year cycles beyond the biological age at which the X-rated finger-rubbing was first shown happening.
Copulation would take place regardless of pon farr, with personal rather than species-specific variation to the frequency and details. But I'd assume Romulans would be a bit more openly passionate about it, and as the result their pon farr would not stand out that much from the rest of their sex life.
(Also, since the Romulans are an Evil Empire, naturally they also force everybody into loveless marriages at an early age so none of the characters we meet is going to have pon farr.

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Timo Saloniemi