In general, you can find all my guides in the pinnen message, including the Frostlands post you already found.
A collection of guides and FAQs Having written dozens of guides, it's about time to put them all together in a single thread. So here's my list of guides and FAQs! As my guides for errors already has a collective thread and is stickied in the bugs forum, I won't include those here. Frequently...
bannerlord-online.com
As for the Wildlands, I never made a specific guide for it but the general area is everything south of the Aserai. There's an official old post of Wildlands and in my collection there is a screenshot of the area inside the Antique Market quest guide.
As for PvE clans, they can be attacked like anyone else while inside of a PvP zone. However, PvE clans can not attack anyone inside the PvP zone. They can however still join their group/clan by clicking on their ally to join the defensive side of the PvP battle.