^ No.
Sample rate is not bit depth. Bit depth is not sample rate.
Yes, most DAWs do their processing in a high bit depth floating point workspace, regardless of the actual bit depth of the original file. However they will do such processing at the original sample rate of the file. One could upsample/convert the original file to a higher sample rate before working on it. However, there is an easier (and generally better, less potentially problematic*) way of achieving essentially the same thing, which is to use the up-sampling option available within whatever plugin you are using (when available). That upsamples within the plugin, allowing it's internal calculations to be more precise without rounding errors, then converts back again. This is often selectable at 2X, 4X, 8X, etc, of the native sample rate of the file, with higher rates requiring more processing overhead. I don't have Izotope RX, but pretty sure it provides such an option. If its actually audible or not it's easy enough to use that, within the processing resource limits of the of the computer you are using.
*There is a Dave Rat video which is close to getting at this directly, yet has a slightly different focus, and essentially reaches this same conclusion.