Is there any "acceptable" g-force threshold in PC?
YouTuber Brothgar has a number of very thorough experiments on subjects like this, which give you hard numbers.
For Gs in general, try
https://youtu.be/RVEd9mcM_CE
For using lateral Gs to your advantage, try
https://youtu.be/PQkTpTpiois
For using vertical Gs to your advantage, try
https://youtu.be/KOkWTeqYBnc
But to generalize, in PC it works like this..... Excitement mostly comes from speed, fear mostly comes from all sorts of Gs, and nausea mostly comes from severe lateral Gs. There is thus a pretty strong linkage between excitement and fear because the faster you go, the more Gs you experience during maneuvers. So, unless you use some of the tricks shown in the vertical G video, it's hard to increase excitement without also increasing fear, and you really don't want to increase fear because that significantly limits your customer base.
Nausea is usually not an issue unless you deliberately build a sickening coaster. However, if you do have significant nausea, you get other linkages between the ratings. High nausea increases fear, and both lower excitement. Beyond various G loads, you end up with lots of fear and nausea and less excitement.
The thing is, though, that ride ratings are averaged over the whole track. Thus, short-duration instants of excessive G forces don't have a significant effect on the overall ride rating, provided there aren't many of them and the rest of the ride is OK. And there are no other bad effects of momentary mondo G loads. Peeps aren't injured, they're not ejected from the trains, and the trains don't leave the track. So really, there's nothing to stop you from having a few really rough spots in the track other than your own desire not to have them.
Controlling G forces, however, is the key to coaster profitability, because of its direct effect on fear rating. Fear rating is the main factor in a peep's initial decision to go on a ride, and all peeps have a maximum fear tolerance that they will not exceed. They also all have a minimum fear tolerance but that acts more like a preference or tie-breaker---peeps routinely go on rides with less fear than their minimums. Therefore, the lower the fear rating, the more potential customers, because even peeps with high max fear tolerances will go on them.
) but, you are correct that the game goes "unrealistic" with lateral G forces. You can go "too far" with G forces, but the system feels pretty lenient right now.