There are a number of issues:

1) Seatpost racks are limited in the weight they can handle. They definitely can't handle full-size panniers fully loaded.

2) Racing bikes have very short chainstays. It may be very difficult to arrange panniers so you don't hit them with your heels as you pedal.

3) Touring on racing tires and lightweight aero wheels can be a challenge. Racing bikes often can't take larger tires because of tight clearances behind the seat tube, between the seat stays, and between the brake arms.

4) Even if you can manage to get the load attached to the bike, racing bikes rarely have low enough gearing to facilitate loaded climbing.

So you need to look at the individual bike. Some "racing" bikes are really more like sport/touring bikes (in terms of geometry) and can be adapted. But generally speaking, the closer the bike is to being truly designed for racing, the less suitable it will be for much else.

RichC