AdvancedSteam is Code plugin to make you easy to implement steamstats and leaderboard, achievement on blueprint. Of course, you can use it in C++. It expands OnlineSubSystemSteam. It fixed some bugs. If you combine Steam stat with leaderboard, achievement, you can create dynamic tables with float and integer stat. You can set/get multiple stats at once. It's fully working as asynchronous tasks.
Steam Leaderboard and stat manual : https://goo.gl/Ia0Cnl
Steam Achievement manual : https://goo.gl/0TCxYQ
Steam Leaderboard and Stats
Steam Achievements
https://forums.unrealengine.com/showthread.php?136370-WIP-AdvancedSteam-Plugin-Blueprint-support