About to order a T520 with FHD screen and one of the i5 processors. My use is web, watching videos, office applications and some light use of Lightroom.

It seems that the least expensive processor should work, but I am uncertain about video and wireless. The consensus around here seems to be to avoid the default Thinkpad wireless card and go for one of the Intel.

As to video... upgrading to the NVIDIA Quadro NVS4200M Optimus technology (1GB) from the integrated Intel GPU adds about 120 to the price. It presumably lowers battery life (not terribly important as I am usually on AC) but not sure that my use warrants it.

This replaces a T43 with the IPS screen, still mostly works but getting long in the tooth, I am soon to lose my access to the EPP, and I need to future proof myself, especially when it comes to possible repairs.
Suggestions?

I have the ThinkPad wireless card in my X220i and it works well.

Given the usage, I think the Intel GPU is just fine.

I'd go with Intel graphics too. However, I'd actually pay a little more for the Intel card, specifically the 6300N - it's is a very good card and it's only $38 or so for the upgrade (depending on the deal / discount going on right now).