Those caps are related to general functions of the soft power circuit. If power from the keyboard button is not possible you must replace those capacitors.
If you upload a photo photo of that corner of the logic board we can say if it has leaked or not.
Its the corner by the RAM and power button, where the batteries are.
If you can’t do surface mount soldering, I have redone my IIfx with great success. It’s a easy board to work on, well laid out.