I realized that 3.3. had not only a new video engine, also a bigger CPU consumption for an empty song. I use a Mac Pro 2013 with 6 Xeon cores and an UA Apollo over thunderbolt, samples buffer 64 samples.
I have 11 % CPU consumption with nothing in the song, thats huge. When i compare it with Ableton Live 9.7. (5 %) or Logic X with one bar (near nothing) on the CPU meter. Both with 64 samples buffer.
Also realtime rendering (export) causes drop outs while the playback is running smooth in the same song.
There must be something wrong in 3.3...