As far as the Facebook desktop app is concerned, you'll be able to keep up with friends and family via Live Tiles. There's also an in-app browser for the News Feed and similar to the web interface, you can employ reactions and stickers to respond to a post, switch on notifications and keep up with events and trending topics. The new Messenger app brings its trademark features like group chats, stickers, GIFs and photo sharing to Windows on the desktop. It also allows you to turn on desktop notifications so you don't miss a note and you can pin a convo to the Start Menu to receive updates on Live Tiles.
Facebook and Microsoft say that Instagram on Windows 10 mobile is rolling out "with all of the community's favorite features." That list includes direct messages, the recent addition of account switching and updated search/explore tools. And yes, video support is there as well. Just like the desktop apps, Instagram also supports Live Tiles, so you can easily keep track of updates on your home screen. All three apps are available for download now via the Windows Store, so you can put them to use immediately.