I posted this in another article and if against rules, please remove.

I bought the X12 with the i7-1160G7 and 16GB of ram. About a month later, I had a major device malfunction and Lenovo offered to replace it with the X1 gen 3 tablet with an i7-8650u and same amount of ram (b/c an X12 replacement would take 2 months).

From what I have read, it seems that the X12 with my current i7 configuration is essentially just a waste of money since it's performance is "locked" due to non-sustainable power consumption limits and that the older X1 gen 3 tablets have better sustained performance. Do I have that right?

If you had the option, would you keep the X1 replacement? Pros of the X12 are the size, weight, battery life, front camera privacy shutter, thunderbolt 4. Pros for X1 tablet are the screen resolution, performance, and SD card port.

Input, thoughts, advice are welcome. Thanks!

Reliability was another issue for the X1Tablets. 

There were driver issues with the keyboard, power modules that broke, driver issues with sound, the laptop magnet was so strong it ripped away part of the keyboard, and the latch system that held the docking bracket on the tablet in place in place would fail.

These were just the problems I found and based on exasperated users looking for help on the web, it looks like the problems were common to the design, and were never completely ironed out in all three generations of the X1 Tablets. 

I don't know about this.

The problem with earlier detachables (not just Lenovo) were the lack of good speakers, good display, large battery, and bad stylus application, not just the inefficient Core M/Y chips on expensive devices.

Last gen X1T3 still had the issue where the hardware was just not up to par with iPads, Galaxy Tabs and Surfaces, when Lenovo was charging almost $500-1000 more (including all accessories and including discounts).

Making it cheaper by downgrading is a good idea, except now it has to compete with the Surface Pro with similar pricing, which has brighter QHD screen, better speakers, more optimized pen, better driver support, better performance, etc etc.
For Thunderbolt, you also have HP Elite and Dell Latitude, which are equally as good in terms of business features.

I love my gen 3. Yes, it is a little large for tablet use; however, the screen resolution is outstanding. That spec made me choose the x1 tablet gen 3 over all others I looked at several years ago.
I would be hard pressed to accept hd resolution in a laptop after using the 2000x3000.