I have recently bought a taylor 310ce, do they come factory with elixir nano 80/20 mediums? Would it make a difference if i was to go for light strings or would i need to get the guitar setup?

it might make a minute difference in volume and tone, and it's always possible you'd need a setup, but i'd say there's a good chance you won't - we only sometimes have to do a setup and all our guitars have been changed from 12s or 13s to 10s. anyway, you can always switch back to the mediums if it doesn't work out.
Taylor's wave compensated saddles allow for changes in string guage without needing a setup. you'll be fine. I've brought my T5 from light acoustic strings to light electric (10's) to heavy electrics with a wound G string (12's) with no intonation, action, or buzzing issues

Dr. Z Stangray
G&L ASAT Classic (Ron Kirn Custom T-Style coming soon! ronkirn.com)
Keeley 4 Knob Compressor
Taylor 314ce
Thanks for the advice guys. Based on what you said bright light ive gone for the custom light pb nano's.