Can't decide between X1, T14, and P14s. Current laptop is dying, please help.

I have reached absolute decision paralysis. My current laptop (Dell XPS 13 from 2016) is dying, the video only works every other time I start the machine, and it's old as hell. Battery replacements are getting worse with each passing year. I use Linux (usually Fedora) and I've been looking at getting a ThinkPad for a little while now. Given the hardware failure I'm dealing with, as well as potential tariffs and the current Black Friday sale from Lenovo, I've decided now is probably the time for a new laptop.

Considering my Dell made it 8 years, I'm looking for something fairly high-end that might last another 8. My budget is around 1500US but I'm willing to stretch for the right options. I have been considering a T14 gen 5 AMD, a P14s gen 5 AMD, and an X1 Carbon Gen 12.

What I like about the T and P models is the upgradeable ram and the price. That way I can order the cheapest model and just upgrade it myself or add to it in the future. Plus I can afford a lot more ram for these than the X1. I like the X1 because it's smaller and I don't like large laptops. The haptic trackpad also sounds nice. My current dell is an XPS 13 and I really like how slim it is.

Whichever model I get will have the OLED display as I have gotten used to the high res display in my dell and that's a deal breaker for me. I will also upgrade the processor to the best I can get considering my budget.

My main question is, how bulky are these T and P series? They look quite a lot thicker than the X1, it seems the entire X1 is about as thick as the lower part of the T and P. I don't need the built in ethernet on the T and P so that isn't an issue as the Thunderbolt 4 will do just fine for my purposes. Are there any other things I'm missing here?

Any feedback or information is greatly appreciated. I can't seem to figure this one out.