If you want a king bed, make that your primary (and maybe only) request.
What view do you have booked? If standard, your view won’t be great. Garden or water view, it’ll be better.
If you’re at BC, it’s more important to request a full balcony if that’s important to you. A lot of rooms only have tiny Juliette balconies. YC, most rooms have full balconies.
So, I’d do the following:
BC - “King bed please. Full balcony if possible”
YC - “King bed please. Nice view if possible.”
I wouldn’t try to request a certain room, since if it’s not available the room assigners won’t know why you wanted it and thus won’t be able to find another room with those qualities.