A:AnswerBased on the games I am playing (Planetside 2 and COD MW - 2019 version) at 1440p I would say it can absolutely play all games at 1080p without lagging.
A:AnswerBecause it's the i7-9700 processor, the abilities to overclock it are quite limited. However, the base frequency is 3.0 GHz, and it can go up to 4.7 GHz with Intel's Turbo Boost technology.
And yes, it does have windows already installed.
A:AnswerThere are 2 fans on the computer and no you shouldn't need another fan, the fans seem to keep the computer fairly cool . I havnt had any problems with mine getting to hot but I just play wow and surf the web sometimes while playing