The echo plus zigbee unit will allow you to control your lights (dim and change colour) however it will not allow you to connect hue accessory items (Dimmer switches, Motion Sensors, etc) if you wish to use any of these features you will need the Philips bridge which I recommend getting in a hue starter kit as its way cheaper and you get some bulbs to start you off. Also the echo plus can't send infra-red signals and so you would still need a harmony hub.
The echo plus (2nd gen only) does have a in-built temperature reader to get the indoor temperature of your house if that interest you but otherwise you don't need an echo plus.
The regular echo has a smaller speaker then the echo plus and no zigbee hub although you can still control your lights and TV with the use of the Philips Bridge and the Harmony hub. The sound is still very nice although if you are going to connect the echo to a amp and Hi-Fi setup I would recommend the echo dot as it can do everything the echo can be with a much lower powered speaker. The echo dot can connect to a amp to give a richer sound via Aux out or Bluetooth and is only £50 or around £30 if you wait until Amazon is have deals on.
In regards to Apple Music, it isn't currently supported but Amazon have said that support will be added at the beginning of next year (2019)
Hope this helps.