when you set an alarm on your phone you have the option of setting the alarm sound individually for each alarm if you wanted to. if you go into clock, and then click on one of your already set alarms, the option for Alarm Sound is there, if you click on the words Alarm Sound, it will bring up another menu where you can use the Bixby alarm, or spotify, and then the last option is where you would pick a sound from the available ringtones in your phone.
For the timer, in the clock app, you click on the 3 dots on right side next to the +, and that will open the settings, under timer is the Sound option, click on the word Sound and it will give you all the different sounds you can use for your timer sound.
