There is not a way to mix the parts. The offsets are different, and everything needs to be much more precise than that to move smoothly.
There are a ton of variables that determine how well a build can cut. So the whole “system test” that includes the whole machine at a certain size will not be easy to perform. And you can imagine it is expensive to build two nearly identical machines and hope to measure a difference.
What has happened are tests on the raw tubes. You can do deflection tests by mounting the tube off a table or between two chairs of a set length, and hang a weight off the middle. The 3/4 conduit flexes more. There is a thread with a catchy title, but it escapes me ATM. IIRC, it pretty much matches the engineering models for those materials too. That will reflect later as the bit deflecting in the material when it reaches certain loads.
All that said, the 3/4" is plenty for a CNC. The difference is just that you will be able to have higher loads without problems in a 1" build. The 3/4" build will still work, but you may have to go slower, or take more passes to finish. For a hobby machine that is idle most of the time, it’s NBD and not worth starting over for.
My advice is to finish the build you started. Learn a lot, and in a few years when Ryan releases something new, either make a second machine or upgrade. You’ll know a lot more and you’ll have a list of things you’ll want to change together.
EDIT: I remembered the name. Quick and dirty test: