As
@Ralston18 , practice and feel. You can utilize sites such as
https://www.typing.com/student/tests to get a feel for how fast you type per minute. The 10 finger approach and learning that will improve your speed but I do know some that can type just about as fast with using minimal fingers per hand so it is individual.
As for gaming, speed is not a critical as muscle memory and knowing where the WASD keys, R key extra is on the keyboard without having to look each time you try to reload a weapon or trying to go to prone position, etc.
As for switches, yes the best method is to go to a Best Buy or Microcenter and get your hands on them. Optical, Liner, Tactical and Clicky all have different feels and likes. Some lean toward optical for gaming, as less travel time, while others will say liner, tactical based on the feel and use of the keyboard besides just gaming. I went from a optical EVGA keyboard to a custom liner switch keyboard for my everyday gaming. For work, I use a tactical (holy panda switches) so I can have the feedback when I'm typing more so then gaming.
A $500 dollar keyboard is in the eyes of the beholder and what you like about it. Some will say a simple $20 keyboard is all you'll need and others will spend over $500 on a custom Group Buy keyboard. I'm a fan of true custom keyboards where you can pick you PCB plate, hot swappable, switches, keycaps, etc. over boards like Corsair. Not that there is anything wrong with them, just a personal preference. Of the 6, I have that are custom keyboards, I think they range from $150 to close to $400 with all the build. Again, this is my hobby and something I like to do so I don't expect others to feel that way or spend that type of money on keyboards. Getting a nice Corsair K70 or HyperX keyboard, could be all that you need versus going down the custom keyboard rabbit hole.
In other words, there is no right or wrong answer, it is what like and want as personal preference.