IBM and Lenovo ThinkPad laptop enthusiasts!
The T480 (at least with the nvidia graphics) is not suited for light gaming. In theory you should be able to play games up to Doom 2016. In practice the thermal throttling is so awful that the GPU is throttled very quickly that you can't even play Quake 3.
CPU and GPU sit on the same heatpipe so that you get to the throttling limit even if the GPU isn't used that much.
don't fixate on the T480, be open to snagging a newer model if the price is right - T490 and T14 G1. even models with soldered-on RAM if they're cheap, like X390, T13 G1, T14s G1; they can be had with 16 GB on-board and they also have interchangeable motherboards, in addition to many other parts being cross-model compatible. unless the price is awesome, stay away from early ryzens (anything below 5000-series) as they're a headache wrt power management in linux. chill with the upgrades, it's the worst time to be spending money on those, your use cases are easily covered with the base config. if you're set on upgrading things, try to source parts from local busted up units and junkers, not online sellers. good luck.
My only tip is buy used. It might be a gamble but it's better than to pay 4x the price. Sometimes used machines are cheaper than the components themselves.