A half-bridge is probably your best option from a noise point of view, and are typically more efficient, but at the cost of added components (size). A forward converter might be ok too, but i havent worked with them much, and they might be just as noisy as a boost/flyback. Forward converter must not have an air gap, though.

For the royer oscillator there *must* be an air gap, precisely because the primary must store a good bit of energy (and ferrite cores suck at storing energy). So the air gap stores the energy.

As far as I know, a half-bridge *is* essentially just an advanced version of forward converter.
Coupling on the transformer is still made as high as possible, and output inductor does the regulation same as with buck converter. So, you did work with forward converters

Royer oscillator, or whatever, somehow seems to care little about the coupling, for it's operation. So you can use a very highly coupled transformer if you wanted a good 'regulation' for some occasions and I don't see why wouldn't it work that way.