I'm new to gog, I have a quick question do I delete the other launchers when finish setting up my accounts?

Why would you do that? Don't you want to play these games no more? Then yes.

If you still want to play them: Don't forget: Galaxy is not a Steam or Epic or Origin or Uplay emulator.
It does not emulate their DRM system.
If you add a Steam game to Galaxy, Galaxy will launch Steam in the background to open the game. If Steam is not installed, the game won't run.

Sadly, that's what I thought how Galaxy worked back then. I was really disappointed when I realized that I needed to open Steam to access the game through Galaxy. Initially, I thought by having it synced with Galaxy, I'd be able to access the game directly through Galaxy. But oh well, I rarely use Galaxy nowadays.

That was never a question for me since I know how Steam works. Valve would never allow a competitor to replace their launcher.
Having one software that can emulate all different launchers and that for a company who wants to sell their own game, if possible DRM free ... not gonna happen.

In my case it doesn't matter really. I only play about 3 games actively on Steam, one on Uplay. All the rest is on GOG. Some I play through Galaxy for achievements, but usually I start everything directly.