No, not Vulkan. Actually almost everyone was complaining about the performance (especially in VR), ED recently announced they found the problem in the terrain engine, when fixed will increase FPS by 50%.
Also, FPS is highly dependent on hardware combination, software optimisation, and OS tuning. Higher resolution is more demanding on your hardware as you probably know. Also, the more apps and services you run in the background can also negatively impact performance. So, more RAM is always useful, in particular when you want to render at high distance views for example, or higher textures etc. Just a consideration. :)
Besides that, I don't know what to tell you. DCS is very demanding.
All you can do is:
- Optimize your system on the software/apps/OS part (services, background apps, page file, power settings, OS/App update settings, etc etc).
- Buy newer, faster hardware
- Lower settings like shadows, visible range, cockpit shadows, terrain shadows, MSAA