Browsers are memory hungry, but based on what you described, you really don’t NEED 16GB of RAM.
Please. Please. Don’t upgrade the 2TB3 model to the 1.7GHz i7. There is no point. And at that, don’t go to the 4TB3 model for the higher CPU clock. Look up videos comparing the two. Look up benchmarks. The CPUs have a variable clock speed, and the cooling on the 2TB3 model is sufficient enough to sustain a much higher clock than 1.4GHz. In most cases, the difference between the 1.4GHz i5 on the 2TB3 model and the 2.4GHz i5 on the 4TB3 model are in the neighborhood of 5%. Not just in synthetics, but in real workloads like video export as well. They are both Intel U series CPUs, and the lower TDP of the 2TB3 model is artificial and is in no way a hard limit in performance.
There are advantages to the 4TB3 model, but CPU performance being a touch higher is more of an “added benefit” of buying the model with better WLAN, faster SSD, and more throughput potential (the 4TB3 model) than it is a reason to upgrade.