I'm going to follow up and find out if the 2021 Cannondale CAADX 1 is tubeless ready. From the information I have, the Schwalbe CX Comp (700x35) K-Guard tires have not changed between the two models, but I am going to confirm that and get back to you once I find out.
With regards to the differences in the shifters and derailleurs between the two models; the 2020 Cannondale CAADX 105 is using the Shimano 105 group, while the 2021 Cannondale CAADX 1 is using the Shimano GRX. I wouldn't say either is better or worse, just slightly different in performance. The 105 group is apart of Shimano's road group, so it's ride and performace is focused more on road riding. While the GRX is apart of Shimano's gravel-riding group, with more of a focus on chain combinations for gravel riding. I want to say, the differences between the two are going to be close and would focus more on the type of riding you are planning. For example, my road bike has a Shimano 105 groupset, and it has offered me reliable performance while riding streets. If you think you're going to spend more time on fire roads, then the GRX might be the better match.
The differences between the chains has to do with the type of drive-train they're complimenting. The KMC X11 is an 11-peed chain for the 11 cogs on the cassette ('20 CAADX 105) while the KMC X10 is a 10-speed chain for the 10 cogs on the cassette ('21 CAADX 1). Each model is slightly different to match the type of anticipated riding between the two. In real world riding, the '20 CAADX 105 can deliver a faster top speed, while to '21 CAADX 1 will respond better to climbing hills. Both will be close in performance, but the CAADX 105 may be a better match for more road riding while the CAADX 1 will match better for "hilly" fire roads.
Hope some of this info helps, and I'll respond back once I know for 100% that the '21 CAADX is tubeless ready.