I’d do exactly what @deirdrebeth said. Start with walnut settings and I would cut the power back by maybe 25% or more. Do your engraving and don’t touch the wood! Have a look at it and see if you want to go deeper. Then run it again and adjust your settings accordingly. Just remember, you can always do more so it’s best to start off conservative. As long as you don’t move the file or the wood the alignment will be perfect, even if it looks off on your screen.
As far as text, the font doesn’t matter if you’re engraving so it’s whatever looks best to you. You just need to convert the text to an object in your design program first.