I ride a CAADX on the bridleways near me and it is great fun. It also goes well on the road and has mudguard eyelets despite being a proper crosser. I can't help thinking that adventure/gravel bikes are just a marketing creation of the bike industry to sell more bikes to the "must haves" If a cx bike is too aggressive just wack a shorter stem on with a bit of rise.
CAADX looks nice although I don't know if it's still available new? Plus I've kinda fallen in love with Planet X as their a yorkshire company and I really like the look of their bikes but I'm not totally committed to buying one of their bikes, at the end of the day the bike that ticks all my boxes is the one I'm gonna go for. And as for your opinion on the adventure bike genre that's what I'm trying to work out, I suppose if their more suited to the longer rides I can kinda get it but as you say you can just change the stem on a cx bike that has eyelets etc anyway. But that just makes the adventure bikes basically rd bikes with relaxed geometry and bigger tyre clearance therefore a cx bike would suit me better being able to handle more technical stuff, fast and gives me the option to change the tyres sizes to suit where I'm riding. things are starting to become a bit clearer now. Thanks guys!