Go out and try it. Probably most you have never a good FPS before (pretty much every popular game made after 2011 or so is awful, in my opinion). Also, yes, you normally have to pay it, but you can get a pretty like game for free, it's called Freedoom, and it works with all the wads (community-made modifications and level packs). It's not a bit memory or processor-intensive, I mean, the game was made to work in 1993 (Windows nor OSX was even out then).
For Windows,
Use
http://prboom-plus.sourceforge.net/ to get the game engine (PrBoom+), and
https://github.com/freedoom/freedoom/releases/download/v0.10.1/freedoom-0.10.1.zip to get the Freedoom .wad files. Open the .zip folder that the Prboom+ is downloaded, and extract it to whatever folder you have your games in. Then, go to the freedoom.zip and get freedom1.wad (Doom 1) and freedom2.wad (Doom 2), you don't have to extract, just copy. Paste in the PRBoom+ folder, should be the first files by alphabetic order (above glboom-plus.cfg). At this point, it's ready to play Freedoom 1, but not 2. Just open prboom-plus.exe and it should work.
To get Freedoom 2 working, and switching off between Freedoom 1 and 2 (and other .wad's) , you must try to open the .wad's by just double-clicking - you probably will get a thing saying that it doesn't know the application to open the file. Set the default custom application to download it yourself at prboom-plus.exe. After that, open prboom-plus.exe and in Options -> General, there should be a choice on one of the pages to use the in-game launcher - it is at default set at Never. Set it to Always. After that, whenever you run PrBoom+, a window should pop up, asking what game you want to play.
For downloading community .wad's, find one, first (pretty easy), and download it. And then put it in the PrBoom+ folder. Then it should appear as a choice to play. Most .wad's are growths of Doom 2, so you should pick Freedoom 2 as game most of the time, and whatever .wad you want to play as the .wad. As an example, you can try with this one
https://www.doomworld.com/idgames/themes/hr/hr, one of my favourite ones (Hell Revealed).
For Mac,
Use
https://sourceforge.net/projects/odamex/files/Odamex/0.7.0/odamex-osx-0.7.0.dmg/download?use_mirror=iweb to get the game engine (Odamex), and
https://github.com/freedoom/freedoom/releases/download/v0.10.1/freedoom-0.10.1.zip to get the Freedoom .wad files. Open the Odamex folder, and put the Odamex folder wherever you want (I put on desktop). Put freedom1.wad and freedom2.wad in the same folder, you can just copy-paste them in. That's pretty much it.
It will start at default with one .wad, but to switch, you open the console (Options -> Console) and type (without quotes) "wad
X" where X is the full and precise to the letter wad name, except for the .wad at the end. So, freedoom2.wad would be "wad freedoom2". For community wads, do the same thing, but you'll have to open the right i.wad (freedom1 or freedom2, usually freedom2) first, and second, you must type the commnuity.wad in the same way as you did for the i.wad, but keep the .wad at the end.
Example: in
https://www.doomworld.com/idgames/themes/hr/hr (Hell Revealed), the community.wad is called "HR.wad" (without quotes). So you would type in the console first "wad freedoom2" and then "wad HR.wad".
.wad recommendations and downloads here
http://www.doomworld.com/10years/bestwads/Detailed (maybe a bit technic) Doom wiki here
http://doomwiki.org/wiki/Entryway
Games aren't made like this anymore - what game do you think would have this muse in it
https://youtu.be/cixW6rogZ48?t=2h6m48s? During a boss battle, too. The biggest problem I have with this game is that it is sometimes maze-like, and that's most other folks' problem with it, too. But it's hardly a big problem - you have a map that updates based on what you have explored, and you can see where you have gone and have not pretty easily, most of the time, anyway. And what game doesn't use a mouse, anymore? The more pointless but necessary buttons you have in a game, the worse it gets.