Fully believe that can’t go wrong with 4 x 5mins or 5 x 4mins at high power (highest you can complete all intervals at, likely min 110% FTP but even that may vary).
Let progression be power increases rather than time. Unless need specific shorter durations for race specific stuff then these long intervals are way forward in my view. If find these super hard then maybe do couple workouts with 2-3 min intervals first to get used to it.
Short on/off (e.g. 30/30) just seem to be a way to make v02 easier which isn’t really the point. We all know v02 sucks, it’s supposed to suck, and if it doesn’t suck then likely not getting v02 benefits!