As for i5 vs i7, performamce wise in your use case, they shouldnt matter much. HOWEVER the new larger battery i think is only included with the i7 model, so you may need to pay more of you want that extra 11% capacity if you get the lower end model.
On the topic of 13 vs 16, only the addons are interchangeable between the 13 and 16 (that is, the expansion cards, wifi if on the same cpu vendor, ram if you only go with intel etc) the mainboard is not compatible between the two models, as well as anything that is designed around the chasis size (e.g screen)
We have no info on the battery for the 16, but we assume that it will have a larger battery given that its target audience is for people who want/need more performance.