What is GNSS Accuracy on a GPS? Is it like if the GNSS accuracy gets lower (3-5m) then the distance from the object you are taking the coordinate increase as compared to a GNSS accuracy of (1-100cm)??
Yes, the Accuracy estimates which come out of a GNSS / GPS receiver are an estimate of the error, but it is important to know that this is statistical - if you look at the datasheet for a GNSS unit, the manufacturer will typically make a claim like "Accuracy of < 75cm using DGPS corrections" - but there will be footnotes saying this is a CEP value (50% of positions captured in 24 hours will have error less than 75cm) or a 1-Sigma / RMS value (68% of positions captured in 24 hours will have error less than 75cm) or a 2-Sigma value (95% of positions captured in 24 hours will have error less than 75cm). And spec sheets often assume static, open-sky GNSS conditions, which isn't how a lot of users actually use their GNSS receivers.
And some GNSS receiver manufacturers do a better job than others in generating estimates, so it's pointless to compare accuracy of GNSS receivers from different manufacturers by looking at their accuracy estimates, or indeed the published specification sheets for different receivers.
If you use real time corrections, you can achieve 10 cm accuracy depending upon the capabilities of your GPS handheld. For example, my agency uses a Trimble Geoexplorer 6000 series and regularly get 10 cm accuracy with real time corrections. We use a wireless hotspot to connect to an online service which enables this, but if your are near many of the government services you could perhaps get them for free or a small fee.