If you install the above mod and follow what I outlined, you will be doing pretty good. I also recommend JRE8. I seemed to have a memory leak with JRE7. I went from 40fps and 20 chunk updates to 40fps and 55 chunk updates while creative flying.
Here are my first tests with improving performance of this pack. Its kind of subjective because it is not data logged and things can very.
1. Pack 'as is': default everything on seed 'abcd'. I let the world full gen and draw around me before going to y:115 facing due S. Status settles at 58-60fps with 13-29 chunk updates on average. I flew forward by 500 z. Status says 48fps with 25-45 chunk updates on average with several spikes down to 1fps and spikes up to 60 chunk updates.
2. Added fastcraft 1.9 with duplicate world. I let the world full gen and draw around me before going to y:115 facing due S. It settled to similar numbers with 47-58fps and 13-20 chunk updates on average. I flew forward by 500 z. Status stayed in the 47-55fps range with 50-70 chunk updates on average with only two spikes down to similar numbers. The world had an easier time keeping up.
3. Added Admin Command Toolbox with duplicate world. I did /pregenspawn 100 and waited until complete (approximately 14 minutes for 40k chunks). Once complete, I restarted. I let the world draw around me before going to y:115 facing due S. It settled to similar numbers with 46-55fps and 40-50 chunk updates on average. I flew forward by 500 z. Status stayed in the 50-60fps range with 50-63 chunk updates on average with only two spikes down to similar numbers.
It was made it very enjoyable. HOWEVER! I noticed that AE2 meteors and Thaum ritual sites are not spawning with the pregenspawn. Time to file a bug report with them!