Typically go for the model coming off business leases, with the slim T model or 13" X model being very popular and well built. The X1 series tends to have cooling issues, so I’d avoid them without a lot of research into the specific model. The P series tends to get run harder, so I’d be a bit hesitant there as well. It seems a lot of companies extended to a 4 or even 5 year lifecycle, so normally I’d be saying to start looking for the T14s g1, of which the AMD models started being very good. But you’d probably be looking more towards the T480s and T490s, still, and I think you’ll probably want to stick with Intel for those. But if you find a good deal on a T14s, particular the AMD model, I’d say jump on it.
In recent models, target the 400nit low power IPS screens. Avoid the 500nit privacy guard screen, which basically behaves like a TN panel as far as viewing angles. The 300nit screen has color reproduction and uniformity issues, but I do have one on my work T14s g3, and it’s not horrible. I have the 400nit on my P14s g4, and it is substantially better.
Thinkpads aren’t as upgradable as they used to be, so be mindful of the RAM in particular.
I have a Nuphy Halo 75 that I’m rather thrilled with. I have a 65% and TKL Leopolds, with Topre and Cherry Clears respectively, that I also love. But I wanted to go wireless, and I wanted RF instead of Bluetooth. I also wanted a happy medium 75%, and the Nuphy checked all those boxes.
I got baby kangaroo switches, as I love tactiles, and I really enjoy them.
A couple caveats:
I was considering a Keychron, but just got the feeling that the QC may be a bit lacking compared to Nuphy. I can’t back that up, and have no idea if it’s true, it’s just the feeling I got from reading reviews.
I also considered a Zoom75, but haven’t had the time for a first build, and availability wasn’t great.
Do you need wireless? Do you need it to be programmable? If the answer to both of those is no, I’d definitely recommend Leopold. They do have some bluetooth boards now, but my experience with bluetooth input devices hasn’t been great.
Varmillo is another one to look into, with the VXT67 in particular looking interesting. That glintstone colorway is gorgeous.