OK, I learned Daz Studio on a laptop that was even less suited for the task than yours (no integrated Nvidia graphics, it has Radeon graphics). I'm actually typing this on that very laptop right now, thanks to the recent failure of the bios/motherboard on my other 'uber' laptop...
It IS possible to make do with a lower end laptop or perhaps a lower end desktop system, but it is not recommended. There's also the possibility of eventual failure of the components. In my case, I upgraded to a high end gaming laptop and the failure wasn't heat related, but the point is that MOST of said uber laptop is now useless thanks to one critical component (thie BIOS/Motherboard) failing. I may be able to scavenge the blu-ray drive, ram maybe, and the two drives (HDD/SSD), but the onboard graphics are now useless to me.
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My POINT in sharing this is you should ask yourself, how important is this laptop to you, and can you easily replace it if it fails thanks to the added wear and tear of rendering?
If the answer to that question is no, then you need to look at building a rendering computer. There are a few threads about that, but right now by far the most expensive component for that is going to be the GPU. Most of us would recommend an 8 GB Nvidia card as a minimum, and 1080 Ti's are about your best bet except for the price (they are near 2080 Ti territory at the moment). You can make do with a 6 GB, but you'll be going 'CPU Only' a lot more than you'd like. Even with my 8 GB 1080s, this happened often enough that I had to trim down the textures and maybe even the number of items in a scene.
Some people do make do with 4 GB cards to start with. The key here is to render your characters separately from the scene in the background, to increase your chances to be able to fit the Iray scene inside of your graphics card. The lighting might not match exactly, but most people may not notice in a number of cases. There are also a number of games (mostly RPG Maker games, but a number of Renpy games as well) that superimpose the characters over backgrounds. Katie's Corruption did this a lot (a Renpy example), and while he did render a few scenes with backgrounds included in the later parts of the game, he still did the superimpose images thing a lot, right up to when he abandoned the game.
Your other option is 3Delight, for which you should get the beefiest CPU you can afford, since it doesn't use the graphics card for rendering. Most products for Daz these days favor Iray rendering though, but it is an option if you want a different look than what you often see around here in the art threads and in many 'Daz character centered' games.
You mentioned a third option - an external GPU enclosure. IF your laptop has a thunderbolt port, this can be a viable option for Iray rendering, but I'm doubtful based on the specs you mentioned. A couple of developers around here have mentioned doing this. There might be a USB 3.0 enclosure somewhere, but everything I've seen lately is built around Thunderbolt. If you are going to need to buy a thunderbolt laptop (i.e. if you current laptop doesn't have TBolt), you might as well build a rendering station. It'll be cheaper than a second laptop, and then you won't need an external GPU enclusure anymore, since you now have a rendering station.
IF you DO have a TBolt port, then an external enclosure is an option. The only question then is, would you be better off spending a few hundred extra dollars for a full computer instead?
There are also rendering farm services that can do the rendering for you in the cloud, but I'm not sure how they'd feel about you rendering a bunch of porn on their servers. My concern here is that you are leaving a 'trail' on servers that you don't own... others can comment on whether they use these, and what their experience has been.
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Hopefully this is helpful to you. Unless you have a usage model that heavily favors laptops, yeah you'll be better off in the long run with a dedicated rendering (desktop) system, but you can make do in the meantime.
I generated a number of renders on this 13" laptop I'm typing on now before eventually upgrading to my now very expensive brick. But it was awesome while it lasted. My usage model heavily favors laptops, but my replacement will be a desktop system.
And if you have a Thunderbolt port on your laptop, and say $300 extra to spare on top of the extra money for a graphics card, yeah eGPU is an option for you.
It all comes down to your hardware budget, which is the strongest determiner of your options. There's always Ebay I suppose, but I'm always leary of used stuff... luck of the draw and all that. If you can't afford a better system, yes you can make do, and at least you have 4 GB of VRAM for Iray renders, so it's not completely impossible. You'll just need to learn how to build scenes to fit those constraints. And of course it'll take longer for those renders. Plus there's the question of eventual laptop failure. You may be able to get a lot of use out of it, or it may fail just when you need it the most... that risk assessment is something you should consider now if you decide to 'stay the course' for now.
I hope that this insight is helpful to you.
OhWee
