I would suggest you wait until after the Microsoft October 2nd event to start with. See what new may be announced.
I am not sure about the Microsoft refurbished deal for warranty replacement. I own a 2017 Surface Pro and I only had to exchange due to something stupid I did in the first 10 days of ownership. They just swapped it out in store and didn't even count it as one of my two accidental damage replacements. But that may vary depending on whether or not you have a store nearby and how new/old the device is.
I get about 8 hours of battery life with the X1 Extreme, which is about on par with what I got with the 2018 MPB I had. The Surface Book 2 gets significantly better battery life due to its two battery format.
Your post is a bit all over the place with the Yoga's, but if I am gathering from the "real estate too small" comments, you are looking at the 15" Surface Book 2? If so that is heavier, not lighter than the X1 Extreme (4.06lbs/1.8g X1E vs 4.20/1.9g Surface Book 2. So if you find the X1E slightly too heavy, it would seem a 13.5" model and the less real estate is maybe your best bet? But if you don't mind the smaller 13.5" screen, you can save about .5 lbs
Yes, I will wait until the Oct 2 event and then decide which one to buy and order immediately. The battery of my MBP 2010 17" is dying. It can' tlast for more than half an hour without an AC adapter. Together with the 3kg weight (laptop alone), it is time to buy a new computer.
I tried both the 13.5" and 15" in a store today and two other separate days. The 15" SB2 is too heavy for me as I also need to carry other stuffs. The 13.5" is not very light but I can handle it given that it has a high screen resolutions. So, the situation is:
1. MBP 2018: Can't stand the butterfly keyboard and it has some issues running Linux. Crossed out from the list. The only case I will buy it is to just for temporary use. As soon as a new verison with a better keyboard comes out, trade in immediately.
2. X1C6 and X1 Yoga: Light weight but the FHD resolution does not provide enough real estate for me. Take 2-3 weeks for delivery. The resolutions of WQHD may be sufficient but the letters may be too small. Without seeing it in person, cannot decide.
3. T480s: looks OK
4. SB2: Good screen resolutions and 10+ battery life. Even at 13.5", I can see words clearly and "seemingly" offers good real estate. Concern about MS giving me refurbrished one if something goes wrong with my device. AC adapter seems to be heavy but probably I don't need to carry it every day due to good battery life. 15" model is heavy for me so I don't consider it.
5. X1 Extreme: Need more user data to know the lengh of battery life for 4K screen. With a 4K screen, it is 1.8kg. If the battery life is not long, I will need to carry an additional AC adapter to make things heavier.
Ideally, I want to try out X1C6, X1 Yoga, T480S and X1 Extreme before making a purchase decision. However, I don't think Lenovo allows so many refunds.