You’ve basically asked how to make an online game. You won’t really get responses to such a wide open question.
To support 100 players, the replication has to be hyper optimized beyond belief. PUBG sacrifices server authority to accomplish this, for example by offloading hit detection to the client. This is fairly difficult to pull off in a secure manner, and often leaves a game open to hackers. In short, no, it has nearly nothing to do with hardware and the server is only one small facet of a much larger paradigm. The game has to be built extremely efficiently, and has to be built with the massive amount of players in mind, every step of the way.
For connecting, you’ll need to do your research. You’ll need a system in place to spawn a server instance of the game, matchmake, etc.
For online player statistics, you’ll need a system in place to record happenings within matches and report them. This is often done with API calls by the game server itself.
In short, if you have to ask this extremely broad question, your experience is likely lacking. There’s no simple answer to such a sweeping question. It requires years of knowledge in many areas to accomplish. The game itself (client/server relationship, what to replicate, when to replicate, culling, etc.), interactions between the game and a web server, pipelines to spawn instances when necessary, etc.
None of this is meant to dissuade you or demean your project/goals. It’s certainly achievable as many games have shown us. You CAN pull it off, there’s no doubt in my mind. There just isn’t a direct answer to your question. There are many, many ways to go about every question you’ve asked, with years of theory behind each. I hope you don’t feel belittled by this post, as it was not meant that way. With time, patience, and lots of research, you can absolutely accomplish this.