I am looking to buy a Pixel 2XL 3rd party. I use T-Mobile and this is the Verizon version. I know it'll work on T-Mobile just fine however are there any differences between the Verizon and Unlocked versions such as timely updates?
They're the same device. The only difference is the VZW version has a locked bootloader. What this means to you is simple: if you plan on rooting the device, get the unlocked. If you have no intention of rooting, it makes no difference which one you get.
IMO never buy a carrier phone over the unlocked version unless you’re looking at a significant pricing differential. Why give any carrier more control over your phone than you have to?