Why clip gain is dangerous in a studio mixing workflow
While the "lazy" or the intuitive cutters and editors on schedule for Video or Audio would argue that clip gain has the advantage of sorting things out quickly, which I fully understand, I still strongly recommend to get rid off this behaviour as soon as possible for many serious reasons. Even on productions on schedule like in a news room. On the end it will cost even more time to repair. The most obvious is that you will loose overview very quickly and will start to mess with the table leg cutting effect while trying to equal volumes of parts of the session later. I cannot count no more the number of sessions I saw where clip gain was turned down and volume turned up in the same channel without any effects inserted in the chain (where it would partly make sense but I will chime into this later...). Second is that clip gain effects clip fades badly and the bits you have for a smooth fade decrease drastically making fades quick harsh or crispy sounding. In a bad way. Test it on long fades with high frequencies. This has to do with the amount of dynamic the fade has when a minus clip gain is involved.
And - To even add more to the issue, well I strongly recommend to not even use clip fades also, if you seriously want to get most out of the signals quality. But this is beyond the borders of this audio engineering note here and is practically not a recommendation for all workflows. Expecially film editing for serial productions need quick edit workflows and clip fades are common practise in all news rooms for good reasons. But this note here is about upper level signal processing and finalizing, so please be patient with my recommendations.
The real and main argument and advantage for clip "gain" - apart from the quick access to change the level on an added clip - is actually the order of signal processing and that clip gain has effect on the level of the clip BEFORE it enters any effects in the chain or the channel itself. And that's where it has its name from. While volume rather changes the signal level AFTER the effects chain. Including the effects. That should actually be the real reason for it (if it wouldn't be still not the best way to achieve this). It makes a huge difference on how dynamic processors and room/hall and other effects react and adds on side chains or bus routings in the channel. Volume does not. But this is actually somewhat unnesseserly messy to achieve by adding clip gain to each clip. Especially in a workflow where others co-work on the mixing stage later or you need a good overview about 400 channels and cutted words on each minute the next day. Which is not uncommon for film editing on the sound mixing and sound design stage. Since "Audio pro editing" cannot work horizontally like film editing and film clips mostly do (apart from effect or green screen layers). In audio each scene has its own group of faders. Otherwise each change could accidently affect other scenes too if automation is not controlled by eagle eyes and automation would become messy very quickly.
If you haven't seen such big audio sessions for film editing you are maybe located in the wrong country. In many countries film audio work is far underrated. Not so in the US and other leading film countries. For good reasons. Psychologically proofed, the audio is even more important for the overall impression today than the video image itself. Simply compare the results in cinema if you have good ears ;-) If you are about to mention silent film here, well, you are pretty right on it. :-) But this is a completely another type of film. And apart from that: No audio is better than bad audio. This is where the silent scream comes from and why it works so well.
Back to the clip gain advantages and why this is the wrong way to do it: This gain before processing is nothing new invented by clips in software editing suites. It is the often overseen little knob on the very top of traditional mixing consoles and is simply called "gain" because of the signal coming in here (gaining the stage). And this is where clip gain has its name from. So gain differs from volume for a traditional mixing engineer since ages a lot and simply by the order of in and out of the channel. And where it is placed on the console instinctively. So you should be careful if you ask him to change gain or the volume. While the long fader on the bottom is called volume on the end of all processing and not affecting any sends of this channel for good reasons, the knob on top changes the level of the signal before and has the traditionally name called "gain" and is doing exactly what clip gain does. But much better. Why? Well because it is better trackable, better automatable, better controllable via mixing controllers and it does not affect the clips own dynamic in case of clip fades. In Pro Tools - the industry standard for film audio work - the little overseen plugin is called "trim" and is exaclty what each fader should have in the beginning of the inserts chain. At least it is in all my works I did for film. No matter if my own or if I help out other productions.
(Needless to mention that this works best AFTER handing over sessions, not before. Or make sure that you share the same plugins in the respective editing suites and DAWs to export/import the gain setting.)
So... To gain the signal before processing in your DAW like you would traditionally do on mixing consoles, do yourself a favour and use a gain staging plugin (like the trim gain plugin of Pro Tools or any similar gain staging plugin in other DAWs) instead of the on some DAWs supported "clip gain" which can be added to audio clips (sometimes called regions or snippets). Each DAW has its own gain staging plugin and there are even free ones around which you can use for that. They all do a better job than the relatively new clip gain feature buzzing around since some years.
First of all because you have more control and less mess and can turn it on and off if required for A/B testing. And second, you should be aware of is that clip gain changes the dynamic range of the signal before it enters the channel and do not work very well with clip fades. Plus, you have the advantage to decide if you want to have at least one insert before gain staging (e.g. Level Meter of the original gain etc).
And last but not least: the experienced audio engineer you co-work with will thank you for that!