well i use a triptop now, and if i wear a tight shirt or something, i kinda feel like you can see something slightly, and i mean it wont flatten it absolutely completely, but definitely the best it will get until actually surgery. also, it depends on the individual person and what size their chest is, and what size/model binder they use, etc.
i used ace bandages before, and those were really good on getting me flat cause i did it tight. but thats about the only good part. it falls down all the time, uncomfortable too sometimes, etc. the binder makes the flattness actually smooth too, so you won't see the edges of the ace bandages and other unsmoothness you see with an ace bandage. also, definitely easier on the ribcage than the ace, at least in my experience.
definitely a good investment if you have the opportunity to get a binder. believe me, you will not miss the lumpiness and falling down of the ace bandages