Does TLP automatically start when my system boots?

Yes TLP will automatically start you do not need to run any command

please check

  0.) General

  TLP_ENABLE=1

Set to 0 to disable TLP (Reboot needed), It should be enabled so leave the default value

Is there a power saving application similar to Jupiter?

If you're not sure you can always check whether TLP is running by typing in a terminal:

sudo tlp-stat -s

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