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On an analog hardware mixing desk it is generally OK to let your levels peak - at least a little - from time to time. The needle jumping above zero now and again isn’t going to cause massive problems like clipping or popping. Indeed, it can add some analog style warm distortion to some sounds. It’s best avoided during mastering, but a little “overing” on the odd mixer channel isn’t a big problem as you work on a track. With digital systems like DAWs however, clipping into the red can be much more serious and is likely to result in nasty digital distortion. Go through your signal chain and check the level at each stage is healthy but not too strong - are you driving one fader really hard but the next one very low? - and you shouldn’t experience clipping in the mixer. Also remember that if you’re having to push any DAW fader right to the top, there’s an issue with poor gain somewhere back along the line.
Automation on hardware systems is fiddly, sometimes even nonexistent on older or more basic gear. In software however it’s a breeze, with all DAWs supporting it. Even some iOS DAWs will let you do it. Remember that automation in software can be used to control practically any parameter, not just fader levels. So you can pan, switch channels on or off, change effects levels, soft synth parameters and a whole lot more. This can make mixes dynamic and interesting in ways that aren’t possible when using hardware.
Your DAW’s plugins might be decent or even pretty good, but a dedicated suite or set of mixing plugs can really take things to the next level. NI’s Komplete for example has an excellent choice of compressors, EQs, saturation, reverbs, delays and other assorted goodies all designed to work together. You can see and hear them in action as well as learning how to use them in your tracks here: https://ask.audio/academy?nleloc=course/3179/komplete-s-mixing-plugins
Maybe you have produced a track on your home system but want to move it to a bigger studio with acoustic treatment and pro monitoring in order to do the final mix. Just transplanting the raw Logic / Live / Pro Tools project is usually a non starter because the studio won’t have all the same plugins as you do, so it won’t work properly. However if you export your project as stems - individual tracks of audio - you will be able to load it onto any system, either software or hardware, as a simple audio-based project. Then, you can mix on that system easily.
Software makes it theoretically possible to mix and apply mastering processing at the same time - typically by strapping a limiter, processing chain or a suite like Ozone across the master buss of a mix. This is something that would be much more fiddly to do in hardware and would not be attempted - for good reason. Mixing and mastering are two separate processes and should be treated as such. Mixing has one aim - a perfect balance of all the tracks - and mastering has another, which is to achieve maximum gain, good stereo imaging and to match multiple tracks on an album to the same volume and feel.