The Luna Mini pack is 2-3/4 by 3-1/4 by 6 inches and 3.3 pounds, about the size of two of the Walmart packs, of which you need four. So this pack is half the volume of the four Walmart batteries but contains twice the stored energy for 4x volumetric energy storage improvement. That is even including the BMS, which is inside that pack! It will fit in any number of little nylon bike bags, or in the triangle or trunk packs I already have, and this pack will be able to be used on three of my bikes (without cutting tiewraps). Mounting this tiny pack is not a problem, even compared to simply tiewrapping four Walmart packs.
The BMS is included in the prices mentioned, and built inside the pack. It is a 30 amp continuous and 50 amp peak BMS on discharge, where the Walmart has zero BMS on discharge in the ebike configuration.
I have a number of chargers that will work with this battery, starting at about $20 or $30, and they are 150W-360W. They work with other batteries I already have, so I didn't need to purchase yet another charger for this pack. Any voltage and current regulated power supply settable to 58.8V can do the task. My favorite is the ebikes.ca Satiator which costs more but gives complete information about the charging energy and voltages put into the pack, so I can keep track of how deeply I'm discharging it and gauge the range and capacity accurately. The Walmart chargers are 15W each, times four for a total of 60W, and they give zero information about energy needed to recharge the pack. They charge quite slowly which encourages the user to not be present when charging. Again the Walmart product falls short of the weakest lowest cost ebike charger, by factors of 2-6x.
The Walmart packs are 1.1 pounds each so the four required are 4.4 pounds for half the energy, plus a wiring harness is needed to connect them in series. So the Walmart packs are 2.6 times as heavy per watt hour. So far the Walmart packs are heavy, large and slow to charge.
Specs for these packs are for 80% capacity at 400 to 1000 charge cycles (so even then far more capacity than the Walmart packs new). The Walmart packs have no specifications (actually the spec they have is a lie, they claim 12,000 mAH and 11V), and the life cycle of the cheap cells inside are typically nowhere near the life cycle of quality 18650 cells. Walmart can choose to honor their warranty or not, depending on their whim when you return the packs. If you warranty one of them, they will be even further out of balance, if you warranty all four of them at once they may decide not to honor the warranty at all. There is lots of fine print in those warranties they can invoke.
The Walmart packs have NO BMS protection on discharge in ebike use, and relying on controller low voltage cutout (LVC) can lead to overdischarging cells within the pack WITH NO OUTWARD EVIDENCE. A few cycles like that, even one cycle in some cases, will destroy the battery. Since there is no BMS during discharge this can lead to using a damaged pack unknowingly with a resulting fireball while riding, whereas a BMS protected pack will shut down before that happens (watching each cell group's voltage), and additionally the 18650 cells have various built in protections that the lipo in the Walmart pack does not have. The controller LVC protection has NO IDEA about the individual cell voltages, it only sees a total. They can be significantly out of balance and still be above LVC. If one cell gets a mere pinhole in the mylar from ebike vibration it can suffer reduced capacity and fireball when the other 11 cells ram full operating current through it at a total pack voltage above LVC (eg 3.9 times 11 cells is 42.9 volts which is above the 42V LVC, so until the per cell voltage hits a little over 3.8V per cell there is NO protection for one cell failing).
By every measure except initial cost, the Walmart packs fall short. Even in cost per use they will likely fall short, but predicting the future is hard.
The Walmart product is somewhat cheap. But it could end up being very, very costly depending on if, when and how it fails. There are lots of ways to save money in life, this may not be the best place for economy. Over a life of say 4 years the Luna Mini costs less than 16 cents per day (a bit more including shipping). It will likely last longer than that so cost even less. I'll use my Walmart packs for starting cars and charging phones and toys, in my opinion they are unsuitable for serious ebike usage. When they die, which I expect will be somewhat after the 2 year extended warranty would be over (do you think it is an accident they offer that period?) I'll recycle them and move on. I will likely gift them out long before that. I saved the warranty investment, very rarely do those warranties pay out. They bring in a handsome profit for both the vendor and the insurance company, in fact. I heard someone just yesterday with an 84 month warranty on their car battery received 25% toward a new battery when it failed at 48 months. And that is only if the new battery is purchased from them, at regular price. Not much value in that warranty. If the pack will start a car then it meets their use case, and it could do that even if the total capacity is significantly reduced and useless for your ebike. Product works, warranty denied. Cheap lipo life expectancy is about 3 years, some of which is already expended in shelf time before the product is sold, so it comes out about right -- for them.
For starting cars these packs are fine - occasional short-term use that is monitored where an incendiary event will be easily dealt with. That is a different use-case and one for which they have been designed (and the protection is provided for in the charging clamp interface box).
Ride safe and enjoy,