A limiter shouldn’t generally be working hard on the master, the problem is when it works too hard it “pumps” too much and the track starts to sound weird, which is what you wanna avoid. The harder you push it the more volume you’ll get but it’s a tradeoff. That’s why I soft clip also cause it reduces dynamics without any pumping side effects, just distortion if you push it too far.
I wouldn’t recommend turning the master gain down because it doesn’t really solve the problem. Without any effects enabled on the master channel, and with the master gain set to 0, you already shouldn’t be peaking in the red. If you are, select all tracks/buses/groups and turn them down at the together till its hitting around -6 on the master channel. (doesn’t have to be -6 really, could be minus -3 or somewhere in that range.) If you turn down the Master gain you’re letting it hit all the plugins, etc while peaking and then just turning down the final output which is not ideal.
As far as utility on the master channel, it’s the exact same as turning the gain up or down on the master fader except it could come before other plugins in your master chain. I wouldn’t change any stereo settings on a utility on the master just cause it could have some weird side effects and you’re effecting the whole song, including stuff you wanna keep the stereo placement mono like subs, kicks etc. Do that stuff on the stereo elements individually or in groups before your master imo. But up to you I guess.
The utility I mentioned between the soft clipping and limiter is only because to soft clip your master signal it has to hit 0. Specifically this is for using the Glue Compressor for soft clipping in Ableton. Any other master processing (eq, saturation, other compressors or fx) should go first, the Glue Comp with range set to zero (this prevents any compression from happening, so it only works as a clipper) and the soft clip button on. Turn the makeup gain on the Glue Comp until the light light by the soft clip button is flicking, and keep going until.you hear it distort too much, then bring it back to where it’s working but still sounds good. Outout of the Glue Comp will be right up at zero, so put the utility after and you only turn the gain to -6 so that the signal out of the Glue Comp isn’t peaking into the limiter. Then put your limiter right after that. Not sure how much difference it makes technically in that case but its always better to have audio coming into plugins, busses and groups and everything at a reasonable headroom - just in case. That said, turning down 18db doesn’t help any more than turning down 3 or 4. It’s the same thing, you just have to turn it up that much more in the limiter until it hits the threshold.
Also should mention when doing this, it’s only going to help so much if your individual tracks still have really big, ‘spiky’ dynamics - you need to address them all individually before you try to squish it all together in mastering. Especially with drums and percussive stuff that has more of a transient. I’ll often do soft clipping or limiting on individual tracks or busses in mixing before it even gets to the master, then again on the whole master. Most of the time (unless you’re using heavily processed one shots to begin with) you can increase the perceived volume compared to the peak volume by a LOT. Meaning that you reduce the volume of the transient and turn the sound up overall. Limiters, compressors or soft clipping are all possible ways, which is better depends on the case, basically whichever has less undesirable side effects. I find you can often go harder on it than you expect. It doesnt matter what the waveform looks like, just whether it still sounds good.
if you want really clean sounding tracks be more conservative) followed by a utility to duck it down 6db again so it has some headroom before it hits the limiter. I usually only have the limiter (Pro L2) where its reducing 2 or 3 db of gain max, set to true peak mode and -0.1db final output. No redlines that way. Not necessarily “the way” to do it but I can generally get pretty hot levels without totally crushing the whole track’s dynamics. If you can monitor your LUFS (Pro L2 has it built in, or you can get MLoudnessMonitor for free from Melda) and compare to reference tracks you like that’s a good clue. A lot of ‘good’ dubstep these days seems to be around -10, some really blown out EDM is like -7 or -6. If that gives you an idea