When I first updated to 2.7 I had a big performance drop. FPS were down 10-15 on average and stuttering like crazy and frame times were through the roof. I played around with settings but the only thing that really helped was backing off on pixel density.
So I started rolling all the things I had done with past "optimization" guides and tips out there. I turned off hags, updated my nvidia driver, Uninstalled DCS and backed up and then deleted my saved games folder. I reinstalled DCS and then cranked my settings back to where they were but ceased using OTT and just set my pixel density in DCS and started flying and everything was flawless and stable. I see some people did this and it hasn't help them, but for some like myself maybe it will.