1. Messenger and Whatsapp
2. HDR (Camera of WM10), always ON both HDR and flash (for the best results)
3. Auto Enhance (Camera of WM10) and Adobe Photoshop Express (specially adding light for shadows of photos)
4 Extreme Music (ads removed, as it seems to be more stable), it will take care automatically album covers and artist photos (if your tags are OK) - if missing, you can add yourself and pin them to start as you like ... and Radio FM Phone, of course (FM Radio 调频广播 for Lumia 950)
5. Others - Deezer (flow), Fi-2 Music Player (specially search of it), Resilio Sync (moving files to/from PC), Screenshot Editor, GeoPhoto (all photos on World map - easy to find all photos based on a place), Voice Recorder (recording calls), Realarm (reliable alarm app), Maps (navigation with offline maps) ...
So that's 5 - I did my best to limit to 5