We have just starting playing with the Echo after we were given a second hand Echo and 2 Dots at the weekend. I have also bought ds a Echo Show with a 5" screen for Xmas to replace his alarm clock. So we have the Echo in the Living Room and an Echo Dot in the kitchen and ds's room.
There are different Amazon devices that all use Alexa - Echo, Echo Dot, Echo Dot with Clock, Echo Show, Echo Spot.
The Show and the Spot have screen which have extract functions such as showing a clock, having a camera call, showing temperature etc. Check out youtube to see what they do.
All will play music, they are linked to ds's spotify account, but I haven't worked out yet how we can play different music on different devices.
For an alarm/clock look at the Dot with a clock or one with a screen. There are new 4th generation ones available this year that are ball shaped rather than the 3rd gen puck shaped ones. 3rd gen ones should be going cheap soon and I expect they will discontinue them eventually, but I couldn't find any 3rd gen with a clock and eventually decided on the Show instead as the price difference between that and the 4th Gen Dot with clock wasn't much.
If you get another one for downstairs you can "drop in" on upstairs and use as an intercom which we are finding very handy, saves shouting upstairs. Or "announce" a message, useful for things such as "dinners ready now".
The other function I am finding useful, if you get one for downstairs is the shopping list. Alexa add toothpaste to shopping list and it shows on the Alexa app.
You load the Alexa app on your phone/tablet and can also use the drop in/announce functionality from there to a Dot upstairs and can view your shopping list (or any other list you have created).
We haven't got as far as using the smart home features yet as they seem to need more bits, but have bought colour changing bulbs (cheap ones that don't need a home hub) for ds for xmas and his Echo Show came in a pack that contained a free smart plug which I hope he can use for the fan in his bedroom with "Alexa switch fan on/off".