At your power and weight, you are better suited to get away on an uphill attack. Staying in the front 4-5 wheels during selective uphill sections is a good approach because the guys with more raw watts can’t just get a free ride across jumping on your wheel. Getting across a gap or immediately responding to a break on flatter terrain is going to be tougher and that’s best done by getting a ride with someone else or jumping from further back. Trying to get away from the group starting ~4th wheel is a tough order if you don’t have a serious kick unless the group is completely gassed.
Also, a big factor for getting in a break and making a break successful is how others perceive you as a rider. If you are not seen/known as a threat, people are less likely to chase you while instigating a break. Sometimes that means they just let you dangle and nobody tries to get across to join you. If you are known contributer/instigator of breaks, it will be harder to get away, but you are more likely to get help.
Honestly, you can read/research all you want and that can give you some guidelines, but the best way to learn is to try things in races. Unless you are already contesting podiums on a regular basis, don’t focus on results. Instead, use races as experiments. I’ve learned quite a few things (and actually ended up with some decent results) from racing dumb and just trying things. Don’t be the guy who analyzes the course, picks the 1-2 best spots to make a move, and then wait for those spots. Hint - everybody is focused on those spots.