Outside garden hose bib plumbing - 1/2" or 3/4"'pex
I think you should take off for the outside faucet from the 3/4&quot; PEX. This will have a lesser effect on the water pressure inside the house than taking off on the 1/2&quot; line that goes to the kitchen. You can always throttle back at the outside faucet if you need to.
EDIT
You could run a 1/2&quot; line to the outside faucet, split off from the 3/4&quot; PEX.