[Samsung Galaxy J7 Prime / J7 On NXT (Exynos7870)] Mightx:
Here are some notable Q&A's regarding the process:

Q: Is my 2+ year old battery going to improve after this process?

A: It's hard to say as it is dependent upon many different factors such as how you use your phone, how many times you run it down to 0%, how often you charge, etc.... In short, it may or may not work in your favor as by this point, you are usually up to your 1000th+ charge cycle and the degradation can be so much so as to warrant a battery replacement instead of any software-related methodologies such as the guide above.

Q: Is there a way to link certain mV readings of the battery to its charge percentage?

A: I'm afraid this is very difficult if impossible and impractical since battery voltage readings regularly fluctuate by significant amounts during use and when not in use, depending on the workload and current draw. As such, voltage readings shouldn't be your main basis, if at all, when calibrating your battery. Sure, the voltage readings do go down when your charge goes down, but from 100%-90% the voltage for Lithium Ion batteries could be 4.2v-4v, and for around 80%-40% it could be around 3.9v-3.7v so the voltage vis a vis charge percentage is non-linear and variable, therefore not feasibly linkable to charge percentage.

Q: Do you really need to wipe the battery stats bin file as the old saying goes?

A: No not really since it has already been debunked that wiping this particular file only wipes the battery usage information such as the one visible from device care or in the settings, not the max or min limits of the battery percentage or anything else of further use. I only specifically included it in this guide so that you could start monitoring your battery performance from scratch and not get confused with your old usage and battery performance, since adaptive technology that uses A.I. such as adaptive battery in newer Android versions base their decisions on your past usage and having your old usage there to base on wouldn't be recommended if you want a fresh start.

Q: Is bump charging (charging to 100% unplugging then charging back to 100% repeatedly) recommended?

A: It isn't incredibly bad to do once and a while, although personally I wouldn't recommended doing so often. This is because with bump charging, you are basically trying to bypass the maximum limitations set by the OEM's as to how much you can charge past "100%" since "100%" on the phone isn't really that, instead it is sometimes around 85%-95% in reality so that you are physically limited from normally charging your Li-Ion battery to true full since this is very bad for its performance, longevity, and goes against its recommended usage. The same principle applies to the phone's "0%" in which it isn't actually true 0% as allowing the user to reach this would mean battery death in which it's own circuitry would shut it off to the point that you cannot recharge it without special equipment.

Q: Why do I see many different ways to calibrate and use the battery fuel gauge reset technique?

A: This is because Samsung hasn't given any official statements nor guides regarding this tool since they only use it internally and why would they teach the public how to use it if the users can just send in their phones to their service centers and they can charge them as they see fit? Well, conspiracy aside, some batteries and phones react differently to certain methodologies in which some phones, after tapping the reset fuel gauge, would actually jump up in percentage instead of normally dropping down. Some can get stuck at a certain percentage and some won't. Additionally, different people interpret the way the fuel gauge reset works differently so different guides can tell you different ways to do it, correct or not. As an example, this guide may not be correct at all yet as long as it works to some extent based on personal experience, then I don't see the harm in trying.

Q: Why is my phone draining faster after doing this fuel gauge reset?

A: It may be because the intent for resetting the gauge is so that it could try to figure out on its own more accurate readings and initially, at least for the first three charge-discharge cycles or so, it is still finding out if the battery should be at this percentage or that percentage. It is sort of like training itself but it should settle down after a few full charges and discharges.

Q: Can I trust battery health apps even if they request root access?

A: This can make them seem legit, but most of the time their effects are negligible at best. Take what they advertise with a grain of salt always. This is since no app can ever truly determine actual battery health and you usually need hardware tools for that since even Android can only say "Good" under battery health and no further details whatsoever.

Q: When I buy a new battery, is it actually new and better?

A: This depends on whether the battery you got was manufactured recently or back when your phone was still in the market. Remember that batteries degrade even when not in use and when stored, so always check the manufacture date of your battery and also check if it isn't some cheap Chinese knock-off imitation (fire-hazard beware!). If you aren't sure, just let Samsung deal with the battery replacement, albeit more costly.

Q: For the J7 Prime specifically, how good can I expect the battery to be?

A: As a long-time owner of this device as long as it first came out in early 2017, I could say that when you have installed recent Android versions through custom ROMS, like Android 9 Pie to Android 10 Q, the battery drain can be much more significant than it was back when it was specially on Android 6 MM since there are a lot more processes, app updates designed for more powerful phones, A.I. technology in the background, and new ways by which the OS works in general so it is tailored for newer and better devices and making it work on this relatively old phone is like running Windows 10 with all its features on a kid's computer from the 90's. Generally, with mixed usage, the phone can last you through the day with a single charge in the morning, with around 3-4 hours of screen on time. When gaming or streaming, SOT can be around 2-3 hours. Standby drain is noticeably worse on newer versions of Android as well. Back on marshmallow, the device can last around 2 days on mixed usage with 4-6 hours screen on time and very insignificant standby drain. Also, note that the device was newer back then so there's that.

Q: Can certain ROMS affect battery performance?

A: Absolutely! I've used unofficial CyanogenMod ROMS back then on my older phones and the battery drain was horrendous with around 2 hours battery life on standby and around 30 minutes or so of SOT! It all depends on how well optimized the ROMS are for the device so always check the feedback and developer's notes before installing any new custom ROM around here.

Q: Why is my phone battery percentage different in TWRP or OrangeFox Recovery than it is inside the OS?

A: This can happen on some devices such as the J7 Prime and other devices from other manufacturers even. I do not know for sure why, but it could be (1), either the recovery or the OS is delayed in reading the correct battery percentage and are out of sync, (2) a bug with the recovery or is device-specific, or (3) the battery needs calibration, although this last one isn't usually the case for phones such as the J7P where this "difference" could appear from time to time even when the battery is already well calibrated.