Can I setup a different signature for each of my Gmail aliases
Yes – you can do that. Here is how to design email signature for of your Gmail aliases is explained in the support note.
Can I have multiple signatures for the same Gmail email address?
Yes – that is possible. You just need to create a “plus” or “dot” Gmail aliases as described here (i.e., create firstname.lastname@example.org for tips, etc.). Then you just need to design a signature for each of your aliases as described in this support note.
Can I have the same signature on mobile?
Yes – you can do that. You will need to have the Mobile Signature option unchecked in your settings and Gmail App will automatically pick up your desktop signature. You can read more in this support note.