Paid presets - in a word, yes. Some paid presets are using stock cabs, others will use the creators favourite Impulse Responses (IR's).
The problem with paying for presets is that what you hear are with the creators specific guitar/pickups and recording gear. These will never sound exactly the same with your gear and will nearly always need some tweaking accordingly.
Building on @grdGo33 response re IR, an IR is actually a little more than just the sound of an amp and a mic. An impulse response (or IR) is a sonic measurement of the sound of a speaker, room or microphone in relation to a sound source. In guitar terms, this is usually your amp. After your guitar itself and the dialled-in tone of your amp, there’s a lot more that can affect your sound. The speaker type, the space you’re in (ie natural room ambience), the build of the cabinet, the microphone you’re using, the microphone’s preamp or position both relative to the distance of the mic from the speaker and its distance from the centre of the speaker. With both single and multi-speaker cabs (eg 2x12, 4x12), some IR's are recorded with several mics at the same time. The combinations are literally infinite.
The idea of an impulse response is to capture all of that information in one go, so you can instantly recall that setting. This means that you can retain your preferred tone, right down to the detail of your favourite mic placement and room sound. The problem is that when you buy IR packs or even use IR's that are available free, you could find that you have literally dozens and dozens of variations of the same speaker. Eg using mic type A/B/C individually or in combination at distance 1-12", offset from the speaker central axis by 1-12". So it's a real rabbit warren and trial & error to find the ones you like best.
Now, even though in Pod Go there is only a distance of mic from the speaker option but no mic 'off axis' option in Pod Go, you still get a good choice of mic types and the ability to alter high & low frequencies and to add a natural room reflection, and a good choice of cabs and speaker options. This means that you already have the ability to vary the tone from the stock cab model considerably.
When you hear an IR compared to the stock cab, your immediate thought might be that the IR is much fuller sounding & bigger eg with more bottom end or 'sparkle'. But one of the reason's is the dB setting of the IR is typically set higher than the stock cab '0dB' setting of the stock speaker, so it's sound is more prominent. But here's a key 'trick' - if you raise the stock cab dB to eg +6dB there's a huge change to how the stock cab sounds and very often you can get extremely close to a third party IR of the same cab.
Some IR's are better than others but there are so many free IR's around, I'd strongly recommend you try these first before deciding to buy. Because we all hear & like different things, an IR that I might rave about you might hate. Similarly, buying patches - you might think these are great but I might hate them. Remember, there are a ton of patches available free on Line 6 Custom tone (I've contributed a few myself) so there's so much to try out before spending money. Buying an IR and/or patches is therefore a lottery.
Why do folk buy? Well, some IR's can be particularly good and some patches might be well crafted. But most often it's because folk want a quick fix - instant tonal gratification without having to do the work themselves. But here's the thing, if all you do is buy stuff you're not really learning about Pod Go yourself and it's that journey of discovery that you'll be missing. And there are a ton of patch building vids on Youtube to help guide you and teach you. But it's still ultimately one persons ears versus another so even a top patch designer's patches, regardless of pedigree, skill in the studio etc, might not suit you.
To make the point, have a listen to the Pod Go demo NAMM 2020 by Phil Hindmarsh, and then load down the exact same patches he was using from Line 6 Custom Tone - Paul is a fab player and in the vid, his tones sound spectacular. Now load those identical patches into your Pod Go - and I guarantee they won't sound like in the vid.
https://line6.com/customtone/search/?submitted=1&family=pod_go&search_term=PH
Phil's skill aside, remember that this is mixed & EQ'd at the board, and your guitar, amp, speakers and even guitar cables or wireless system will be different. And everything impacts on your tone even down to the type of pick you use!
And if you are a gigging player, remember that patches which might sound great in your room at home through headphones or your own home amp might sound 'meh' or even bad live in a band mix or through your gigging amp at stage volume or even if (like me) you don't use an amp and put your MFX straight through the main board/PA. And vice-a-versa ie great gigging patches might sound bad at home. And all those fine nuances as between 1" or 3" off axis etc that you might discern at home through headphones - well, & trust me here as I'm a gigging player, they go straight out the window as you'll never ever hear such differences in a live band mix. And all the reverb, delay & distortion settings that sound great at home - chances are you'll need to take everything down as in a live band mix you need tones that cut through the mix and don't sound muddy or washed out.
There's a thread on this board on IR's, including posts from me with links to free IR's - so do a search and check that out to get you started on IR's. Remember, learning about tone & what your gear is capable of is a journey, and that folk selling IR's and patches want to make money. I'm not saying don't buy stuff or that there isn't some good stuff out there - but there's a lot of free options to get you started and there's no substitute for learning at least the basics yourself.