Same here.
Laserdisc games will use the Daphne emulator but unfortunately that is a bit of a pain in the ass to setup. Though if all you really care about is Dragon's Lair 1 & 2 and Space Ace the Dragon's Lair Trilogy for the Wii is easily setup and plays great.
For the vast majority of arcade games you will use Mame, either the stand alone version or Retroarch core is fine. Which one you use will come down to personal preference, I like the stand alone version myself.
All the stuff in this time I suggest and recommend Retroarch.
PCSX2 emulator for PS2 and PPSSPP for PSP.
Most HD space will be taken up by the CD and DVD based console games, those disk images get fairly big.
This is certainly doable and using your arcade controls shouldn't be much work at all, especially if your arcade stick is detected as an Xinput controller. If it is something like the X-Arcade it may take a little more effort to setup because it is not detected as an Xinput controller but rather as a keyboard.
Retroarch is a multi emulator but RocketLauncher is mainly a backend for HyperSpin but can be used with Launchbox for more advanced features. I personally don't use or like RocketLauncher but there are others around here that do. If you decide you want it you will have to look at learning how to set it all up and I won't be able to help you with it.
Definitely the best way to approach it.
That will depend on the system. For Mame and cartridge based consoles it is the easiest. The Mame roms work it is easiest to just get the whole set because how parent and clone roms work along with bios files, it becomes a real mess trying to pull out individual games with its required parents. Cartridge based consoles rom sets a very small and easy to get full sets, when looking for them search for "No-Intro" sets. These sets have all the games without all the extra fluff of "GoodSets".
CD based game sets though get to be quite large in size so for those I recommend just getting the games you know you want to play. If unsure of games look at some videos on youtube of "top games lists" Metal Jesus and Gamesack have some great videos showcasing a lot of games to get you started out.
Primarily this will be done in the emulators themselves and no it wont be on a game by game basis. With Mame though you can set up a "default" controller set up but of course due to the nature of arcade games this wont always be ideal and you can and will tweak some individual games controls. Launchbox does nothing with the games controls.
Some rare instances of this may be required such as with Daphne for laser disk games but it really is the rarity rather than the norm.