Hi,
As a bigger rider (193cm, 89kg, 330FTP), when is it best to really push in a road race?
From what I understand, when riding uphill, the majority of effort goes to overcoming gravity, which is a downside for heavier riders. When riding on flats, gravity is negligible, but wind resistance plays a more important factor.
If I want to optimize my strategy for creating a gap, what would be the best use of my energy?
are we the same person? same height and weight. similar ftp. if your rider profile is anything like mine maybe getting in a 3 or 4 man breakaway is the way to do it but dont waste your energy if someone else is not doing their turn on the front. if you can get a reduced sprint and you still have some left in the legs there’s a good chance you’ll outsprint your opponents. when you know a short climb is coming, try sagging. get in a good position near the front and slowly move back through the bunch. you might be able to save yourself 20w+ than if you tries to maintain position. being taller we are like sails in the wind. get good at getting as aero as your can while maintaining power. Learn positioning in the bunch and when and when not to move up. conserve enrgy where you can, draft as often as you can and finish them with raw power at the end with a 1700w sprint:)
Guttering people in the crosswinds is a time honoured tradition for the big riders.
+1
I find that lighter riders tend to ease up when they’re not climbing so I would make the break cresting a hill, keep the power on into the descent and on again into the flat. Preferably when the rest of the profile is flat or rolling.
Crosswinds and attacking a pedal-y downhill are both good for you probably.
Cross winds are great for ripping groups apart and minimizing draft, but there is usually not much element of surprise with that tactic (everyone knows it’s coming). I’ve actually found strong tailwinds (ideally cross/tailwinds with false flat) to be good opportunities to string out a group and cause splits. You can often catch people sleeping on tailwind sections with riders sitting too far back in the group. By the time they realize what’s happening at the front, splits have formed and/or people have rolled off the front.
Cant say whats good for big riders through experience, but as a lightweight climbing type, I can tell you when I really dont like having to chase them lol
Over crests & downhill - Your weight is an advantage here & its tough as hell to keep up.
Long flats - Raw wattage is king and putting a solid effort in means I have to go uncomfortably high to stay in your draft. Once out of the draft, Im absolutely screwed
1-2% false flat downhills with a cross tailwind. Absolute kryptonite for a light rider. They might actually require MORE watts than you to hang on 
In addition to what was mentioned above (over the top of hills, crosswinds) - if you can attack in a crosswind right before a corner when it turns into a tailwind that works really well.
A tailwind can negate some of the benefit of the peloton and as a bigger rider you might get a little bit bigger boon from a tailwind than smaller riders.