How can I remove unneeded playback engines?

You go into the Unity install location for example: "C:\Program Files\Unity5\Editor\Data\PlaybackEngines" and then delete the folders which you don't need.

I deleted the IOS and Metro ones - for some reason together it took up nearly 5 GB! I would urge the Unity developers to allow the option to exclude unnecessary modules in the future.

When I deleted the folders after I opened Unity I went to build settings and Saw it said no IOS module was installed, so that looks good so far.

I noticed that now my Unity installation is only 3GB and it loads MUCH faster!