What are the main strategies to maximise the benefits from this item?

I think the main purpose of the original item is just to be able to maximize the weight of all the weapons a character might be holding. So it will help keep you flush with ammunition. Another thing it helps with is keeping your weight down, though not all campaigns are run with encumbrance in mind so you might see that benefit.
In one of the Adventures of the week https://www.dndbeyond.com/posts/402-encounter-of-the-week-the-dying-unicorn
It was suggested that you can give the ammunition slot a temporary +N bonus depending on the character level which is kind of cool.

Off the top of my head,  since it's a bag of holding sort of item It could also potentially be used to sneak in weapons into a place.

One advantage of the Quiver of Ehlonna vs the Bag of Holding is the interaction rate. The Bag of Holding takes an action to withdraw an item, but you can draw from this quiver with no additional delay. This makes it a lot more versatile for characters who might use multiple different weapons or ammo types, but don't want to carry too much weight.

Be a level 10 artificer who can make this with their infusions. Have another infusion be a bag of holding and a homunculus. Have your homunculus carry both items to the BBEG and place one inside the other for Astral Plane shenanigans.

But it says "You can draw any item the quiver contains as if doing so from a regular quiver or scabbard" so doesn't it still take an action to draw a weapon from a scabbard? 

It would be a free object interact (unless you had already used your free object interact, in which case it would be an action) because drawing a weapon from a scabbard is one of the uses of your free item interact.

Quote from Penanghill >>

What are the main strategies to maximise the benefits from this item?

 Put weapons in it. Remember "arrows or similar objects" includes things like daggers and wands, most one-handed weapons qualify as "javelins or similar objects", and both greatswords and longbows qualify as "long objects".

Because drawing things out of this is the same as drawing a weapon (free item interaction), rather than retrieving from a Bag of Holding (1 action), you can use this to carry several situationally-appropriate weapons (or magic items), and use this to hot-swap between them as needs arise.

Alternatively, you can fill it with a bunch of items you would otherwise leave behind without taking up precious weight in a Bag of Holding or space in a Haversack or Portable Hole. Then you have more stuff which can, for example: sell for money, arm random peasants, forge into better stuff, become Tiny Servants or Animate Objects, feed a Rust Monster, etc., etc..

what is the point of this Quiver vs the Efficient Quiver?  They have exactly the same description.

From my understanding the point is 'Ehlonna' is a copyrighted name {I believe she is a goddess in the Greyhawk setting if google is to be believed} , and could not be given away in a free book/SDR without there being possible problems. Hence they renamed the item to Efficient Quiver in order to avoid the issue.

You will find similar situations with spells such as Nystul’s Magic Aura renamed to Arcainst's Magic Aura.

Well, the spell Flame Arrows affect all of the arrows or bolts in a quiver, and this DOES hold 3 times the ammunition of a regular quiver RAW. The spell lasts a whole hour or until you use all the arrows in it once, so if you're really pumping out the damage, Flame Arrows WILL run out before the time limit but you'll get 3 times the benefit. Battle Smith Artificers, Edlritch Knigh fighters, and Rangers will get the most benefit out of it.

Has anyone encountered using this to store rolls of  coins / cylinders of gems ? There is no weight limit specified like a bag of holding.

hey i love this item

Could a musket fit in the big pocket?

The plural of Quarterstaff is Quarterstaffs (no apostrophe).

Pretty neat if you have a couple of staffs.

This should be a common item. 

It's uncommon due to the magical nature of the quiver. In real life, all the arrows, javelins, bows and others would be too bulky or heavy. This quiver both minimizes space used and only weighs two pounds (less than one kilogram).