The PC Requirement for PUBG is different for bot PUBG PC and PUBG PC Lite.
As mentioned in the above link for "recommended" system requirements,.. the game is vary taxing in areas during game play, the maps are not optimized vary well and require "recommended" hardware for smooth gameplay.
The "minimum" system requirement's according to developer Bluehole for AMD hardware : AMD FX-6300, 6GB Ram, and AMD Radeon HD 7850 2GB.
Asking why your having issues playing the game running,.. A10-7800, R9-270, with 8GB system memory,.. while I can assure you the 8GB system memory is not the issue for your rig not running the game smoothly.
Playing any modern game today, with older hardware that is rated at or near minimum requirement,.. is going to disappoint you.