If the shoots are green, they do break easy. I have pulled green shoots down, but you just have to go slow, and pull a little at a time, tie off, let it set, then pull a little more, etc. There is nothing wrong in waiting till they are stronger. You shouldn’t have to wait till the end of the season though.
Sometimes I have bent a branch downward pretty hard, while holding where the branch is attached, so that the force of the bend is not where the branch is attached. By bending the branch hard like that, it damages the bark on the top side where it is bent, and sort of stays more bent down that way. You have to be careful doing that, or you can also break branches.
You could go ahead and prune a little on the nects. Just don’t over prune those. I think the pom pom look is coming because you are pruning sections of wood completely bare, which gives you lots of blind wood. You don’t have to do all heading cuts, you can do some stub cuts and leave a few buds at the base of a shoot you stub back.
That way you won’t have so much blind wood. If you don’t like the way the stub is growing, you can always come back at a later date and cut the stub out.
I might prune some of the upright stuff on your cherry plum tree to get it to spread more. Plums are actually a little easy to prune that peaches/nects because they continue to form new buds on blind wood. The foliage on plums also tolerates shade a lot more than peaches. If peach shoots which are too shaded tend to die, whereas plums (like many other fruit trees) will tolerate a lot of interior shading without aborting the shoots.