I've toured on lightweight racing bikes for years. always used a bar bag + pair of panniers at back. 23c race tyres and 36 hole openpro rims are perfectly good enough if you are a smooth careful rider and keep tyres pumped up properly. - but ideally go for touring specific tyres for peace of mind.
always take a proper pump (not mini) + 2 spare tubes etc.
take a new pair of shorts for every other day + baby wipes + antiseptic cream to keep sores away (depends on type of touring, i..e if roughing it and thus often can't wash)
Use threadlocker on bolting up attachments (cages + pannier racks) otherwise they work loose.
instead of carrying heavy/bulky air mat/roll mat for in the tent - look for bracken/long grass etc. near your campsite and put a nice thick layer of it under the tent before you erect it... comfy & cosy!
bar bags are best when you can put the map in the top for easy access on the move. ideally they have special waterproof clear cover to protect yet still see the map.
pack clothes and sleeping bag in waterproof stuffsacks that compress (Pod Airstream Lite Drysac - uses an eVent section to allow air to be pushed out but no air or water in)
if you can possibly do without it, then don't take it.