Quite liking the look of the new boardman cx bikes. Having never had a cx bike how does sizing work?

I typically have a mtb with a 22,5 to 23″ effective top tube Typically towards the lower middle!

What would be the equivalent cx size and if you are on the cusp of sizes is it better to go large or small

Sorry if this is a dumb question !

And before anyone says try one they aren’t in the shops yet 🙂

Never mind all this TT stuff. How tall & inside leg?