[mst]

There's no switch "Corrections on" in any RAW convertor that I have used. Maybe in some pedestrian ones, there is such thing, but most of them allows you to selectively apply individual corrections, and to a certain degree. And even if you have enabled them in your camera, your RAW convertor might decide to apply different corrections on its own. And this will not modify the RAW file, but the rendered JPEG/TIFF image that you export based on the modifications that you have made to the image.

That's not correct. Almost all RAW converters automatically apply more or less the same corrections if it is part of the system philosophy/manufacturers decision to rely on software correction. Only a few of the converters offer an option to switch these corrections off completely.

In any case: of course the correction is not applied to the RAW file, but on the result you have a look at/print/share online/give to others. Software correction of distortion always comes at a price (lower resolution), no matter if it is done in-camera or in the raw converter. The algorithms might be different, the results may vary between several products and compared to the in-camera conversion, however the loss of resolution is an unavoidable fact. The higher the distortion, the higher the loss of resolution.

That's why I prefer correction by glass over correction by software.

CA correction is a different story, because it's a fairly easy correction and yes, usually has a positive effect on the perceived sharpness (except for excessive CAs).