I completely understand your excitement about visiting lesser-known spots in the Philippines beyond the usual tourist destinations! Another place I'd highly recommend is the island of Romblon, particularly Sibuyan Island. It's often referred to as the "Galapagos of Asia" due to its incredible biodiversity. You can hike Mount Guiting-Guiting for an adventurous experience or relax at Cresta de Gallo, a stunning white sandbar.
Don't miss visiting the Banaue Rice Terraces in the north if you can. Although they're not exactly off-the-beaten-path, many travelers overlook them for beaches. They are a marvel of ancient engineering and provide a fascinating glimpse into the country's cultural heritage.
Regarding customs and etiquette, showing respect is vital. Using "po" and "opo" when talking to elders shows courtesy. Try saying "kumusta?" (how are you?) when you meet someone, it often starts delightful conversations. Additionally, be mindful of personal space and use your right hand for giving and receiving items.
As for travel tips, ensuring your itinerary includes flexibility can be helpful. Transportation in remote areas may not always run on time, and weather conditions can affect your plans, especially during the rainy season.
Feel free to explore more about each destination online or join travel groups to get local insights from residents or other travelers. If you’re curious about anything else or need more recommendations, just ask! Enjoy every moment of your adventure in the Philippines.