The advice that
@huntnful shared is absolutely solid - think in terms of shot angles, and how to move yourself into
them, as opposed to getting right up in the buck's bedroom. This includes thinking ahead to where they'll be when feeding along some sort of path, and finding a shoot angle/location that you can get into in enough time for when they arrive.
Regarding rifle and cartridge - There's a famous/infamous thread on there for .223 successes, that includes grizzly, walrus, and elk, along with other threads for .243/6mm, and .25 cal. The evidence for capability of even ol' .223 is encyclopedic.
If I were to summarize bottom-line lessons from all of it, it's that
1) Shot placement matters more than anything,
2) Only practice gets you excellent shot placement
3) Low-recoil allows for a lot more shooting and less likelihood of developing a flinch, allowing for more practice, allowing for better shot placement
4) Bullet construction matters far more than casing dimensions in actually doing the killing - an excellent small bullet placed well kills far better than a magnum freight train missing the vitals.
In short, choose the setup that you can absolutely shoot the most, as often as possible, flinging the best bullet for the task at hand, with reasonable inherent accuracy built into the gun and ammo loading. You have an advantage in choosing a cartridge wisely, because as a bow hunter you understand that even a sharpened razor blade on a stick will kill extremely well - if you put it in the right spot. Now, just find a cartridge you'll enjoy shooting a hundred or more rounds out of your gun at a time, so that you can do that at greater distances.