New Z3 owner full of doubts

I've been quite used to flashing ROMs, but I had a Nexus 4 for the past few years and I am quite lost regarding the Z3 state in the development field. Could somebody answer a few questions?

1. Is there any Newbie Thread where I could read everything regarding flashing, restoring, backing up DRM keys, etc? Nexus 4 was quite simple and I am really lost with these new Z3 concepts.


2. I have a Z3 d6643. Can I flash a Z3 d6653 or 33 or 03 ROM? How does the model number influentiate everything? Can I follow all the steps for other model numbers without any problems on my phone?


3. Are the AOSP, CM, non-sony builds any good? Or should I stick to sony-based for a great experience?

Thanks in advance!