Workers are not very productive unless they're allowed to visit the pub often. Same thing with trading, think of enjoying a movie as the trading beer. You won't be productive unless your portable device can give you that "beer" experience. 15.6/16 inches still too small to enjoy movies. The optimal portable screen size for trading purpose 17.3 inches.
For many years I used a 17" MacBook Pro and I loved that thing. I was so bummed out when they discontinued it.
When it is time to trade, you trade. When it is time to drink beer , go drink beer. When it is time to have sex, go have sex. Many people have serious problem concentrating on trading. So they resort to multi tasking. Good luck to your tiny screen. Meanwhile go learn how to concentrate on trading. Most traders cannot do it. It is very easy to do multi tasking (with disastrous trading result). It is very difficult to concentrate on just trading and trading only.
The standard size business laptop is 14". It's best to keep your tech footprint at a minimum when in public a lot. Also, setup and takedown time should be minimal. Heat 1995, 30 seconds - YouTube
This is the ultimate gear on the go. https://www.mediaworkstations.net/systems/portable-amd-workstations/a-x2p/