Hi,
I was wondering if -6 dB gainer on master track before limiting the whole mix is worse than having no gainer at all and you’ll adjust gain separately on each track. I made a new version of my song with no gainer on master track and I think it sounds a bit better. Also +1 dB boost in renoise’s maximizer gives a slight more sharp sound on the mix. Could be that I just made a better dynamics mixing when adjusted the dBs lower on each track. What do you think?
if it sounds better, it probably is better . . . . 
A gainer at -6db on master would work as a limiter wouldn’t it? My own experience with limiters on master is that you get a lot of unwanted volume changes if you don’t mix track by track properly first, like if you already put the limiter on the master, and then add a synth with too much bass (f.ex). You wouldn’t neccessarily notice that the synth is too loud. The too loud synth-sound would then cause the rest of your mix to be… hmmm. how should i put it… toggled down in volume to make room for the synth.
I’ve had this happen myself in various tracks lately. It sounds all well and good when I’m sitting at home trying to mix it all properly, but I’ve got access to a club pa-system, and when playing my tracks there you can really hear the limiter having an unwanted effect on the mix.
But!!, and I can’t stress this enough, I really really suck at mixing and mastering. It’s my biggest problem when it comes to music production. But in my own experience, limiters might seem like an easy way out, but without proper work put in before turning to the limiter, you most likely will mess your mix up. Or maybe that’s just me 
Edit: I should add that I still haven’t figured out how to do the “proper work before adding the limiter”. I’m working on it. But dammit, getting stuck on trying to make it sound good really takes away from music production itself. But it’s gotta be done I think…
I personally just shove a maximizer on my master, and leave it at default settings. This acts as a brick wall limiter, preventing clipping, but doesn’t chance the general dynamics of the track. Sometimes, when my track is excessively loud, I need to negative-gain the mix before it hits the maximizer so that it doesn’t compress the shit out of it.