TBH I quite fancied doing one of the "established rides" but plotting my own sounds good too.
Exactly the same position I was in when DIY by GPS came in. Then I spent many hours mucking about on computers with routes trying to get the distance right, not too much and certainly not too little, plus decent places to rest and eat, trying to get quiet roads, not too many hills, etc etc.
Then I realised it was a lot easier to bung a few quid in the post to El Supremo and ride something someone else worked out years ago. And once I found something I liked I did it the other way round. And in different weather - it always felt different. We're lucky here in the south-east - we also have the Grimpeur du Sud rides and the Fairies' events.