absolutely true, and good advice, almost all road surfaces on the WAW will be very rough, think northern Scotland, as they are mainly tar and chip / chips sealed minor roads so that traffic is minimised. only very short sections will be good quality and smooth; they almost seem like 'teases' and dont last very long.
some tips to cope;
very good seat pads in bibs, is essential.
double wrapped bar tape is essential.
unless you want to try 'win' the thing, id go for reliable strong wheels rather than the lightest wheels;
id avoid deep section wheels also due to weight and wind buffetting on the exposed coastal roads (~75% of WAW!!!).
pair the wheels with 25 or even 28mm tyres, a bit of kevlar protection is probably well advised also
damper on seat post would be advantageous, canyon used to use a split seat post on their endurace and early ultimate models from ~2016 they claimed was very good
tightening bolts, screws etc every couple days, those roads will loosen anything, even thread locked bolts find a way of coming undone!
It's certainly a cracker of a route. I think the raid version will make a significant difference to the experience if you aren't at the fast end of Audax. Sunrise 5am, sunset 10pm; plenty of opportunity for riding it entirely in daylight if you are up and away early enough each day. Three to four hours less riding your bike per day, compared to the "classic". Opportunity to adjust how far you ride each day , as long as min average distance / speed met. It'll all add up to reduce how much abuse you give your body day after day.
17 hours of daylight seems like enough even for riding 300km a day, because if it isn't the sleep deprivation will be brutal.
Eamon, in 16, warned us to treat 300 as though it was 400 on WAWA. It was wise advice.
The road surfaces can make British roads seem smooth. Not potholes just rough surfaces on the smaller roads. My GPS mount broke on day 3 due to vibration. Though Ring of Kerry (day 2) with EU money has nice surfaces. Fit as wide a tyre as you can within reason, and as low a pressure as you also see fit.
Nadgery as above
The winds can be brutal riding out on the headlands. Think Dutch hills combined with real coastal hills.
On Sunday I'll post a couple of short videos I took of the winds on WAWA 16.