It seems like it would make sense to do intervals at a cadence and power that mimic what you're doing on a HC, but I know nothing. Maybe mix it up with Russian steps or something? And surely sticking some sweet spot/tempo 'recovery' stuff would be good to maintain your base fitness.
But maybe doing longer threshold intervals that dip into VO2 max would be more beneficial. As far as trainerroad stuff goes, have you looked at the crit specific plans? They would presumably offer more short, hard effort specialism.