Nope. You can't do that as eu rom and official rom are two different families of rom.
Take my humble advice. Stay at eu rom 8.2.3.0 likes I do. This rom is the best and super perfect.
The new Android 7 based rom is basically still unpolished at this early stage. Few critical bugs are as below:
1. Auto/Manual brightness bug.
2. Ringtone and media profile bugs for speaker and earpiece modes.
3. WhatsApp doesn't recognize custom tone. (No sound if you choose to use custom tones. Only stock tones produces sound).
4. The volume scaling between different types and sources of playback is inconsistent too.
5. The overall performance and speed of 8.5 is less than desired yet.
No rom beats eu 8.2.3.0 at the moment. Just my humble opinion.