Hey, I’m still using studio one 
In touch with support
It’s not about which DAW you are using, it’s more about the mastering chain and orders of plugins, at least in the software domain, I would love to help you mix and master your tracks for great price if you will need to do some!
If so, let me know at: https://www.fiverr.com/thetopmastering/master-your-tracks-for-best-price-and-quality
I use Pro tools for mixing and Mastering and recording its what i learned first. I also use Cubase pro as well. I love both DAW. At the end of the day use whats best for your work flow. Not all DAW are easy to use. But if your use to a certain DAW then stick with it… At the end of the day your want to just use the DAW as a car to get the Finished product that sounds amazing… 
I’ve had a similar issue with performance in S1 4.5 on Mac Pro 2.7hz 12 core 64mb ram. I was really liking it for mastering but I started to produce something and got to about 12 tracks with the NLS channel strip and it was grinding to a halt. I had to freeze quite a few to get any performance back. Hardly anything showing on cpu usage. I can get 3 times that at least in Logic X before I even think about freezing tracks.
I found it quite buggy too, some times just instantly disappearing…
I’ve been using Audio Unit plugins and @Paul recommended I try VSTs, which I will.
Otherwise back to Logic X for production and mixing and S1 for mastering I think.