Question Slightly less casual gaming + battery

Jul 16, 2019
This seems like the right kind of place for a good dose of common sense, so here goes.
I use a UX430 Zenbook for school and work, and long battery is important to me. Recently, I got into less casual gaming (I don't do 3D, shooters or that sort of thing. We are talking emulators for up to PS2 or DS, and games like Secret of Mana or the other Final Fantasy games). My computer's battery goes down to an hour or two when I do this, and understandably so, but the important thing is that otherwise I still get 8 or 9 hours, even now after about two years of use.
The problem is that these games can lag or run slow (at times) even on minimal settings (when they exist), and even when plugged in. The computer has an old SATA III SSD, an i7-7500u, and integrated graphics.

I would like to replace it with something that can run these games smoothly, without going so overboard on the specs that I don't get good battery life (especially when not playing games). I will emphasise that a smooth game is far more important than a pretty one - I am happy running at minimum settings so the game doesn't lag. What kind of hardware would improve on the lag without compromising on the battery - is a basic MX150 or the like enough (or even, perish the thought, an integrated Vega 8 or 10)? Do I need to go higher- 1050 or 60 etc.? Would the uograde to a modern PCIe SSD improve things (or not), or an 8th gen Intel or 3rd gen Ryzen? I don't have much money to throw at this (but I can wait for a spectacular sale). Aside for hardware advice, can anyone recomend specific model(s) that would do the trick?
Yeah, weight is a plus, and I want a 14" or a light 15", but light is relative - I don't expect miracles, so call it around 4.5lbs or less or so (for 15").
Thanks in advance!

P.S. The UX533FD-NS76 is totally overkill, right? Not that I have $1150 to spend right now, but just asking.