but one thing is, since we have saw some other manufacturer are able to really minimize the crease, somehow Sammy still not really able to reduce it this version? Maybe the next version?

New Fold3 cheap or 2nd Fold3 cheap?

Not often.. as far as i know only one person Fold3 have bubble problem and two person have a Flip3 screen protector problem in this forum thread. This means it is not a common problem.

I'm using Moon+ Reader Pro on the Fold 4.
Works great on it. You can set it into 2 page layout or single page on the open screen.
I'm using it on a single page mode for the ease of reading.

Rest of the app features works as normal.

It renders the S Pen to be non functional on certain part of the screen.

Any third party nice casing for Fold 5 with SPen to recommend?

One of the upgrades we had hoped the Samsung Galaxy Z Fold 5 would include is a dedicated slot for the S Pen. The idea being that you can slip the stylus inside the phone, Galaxy S23 Ultra-style, rather than having to use a case that costs $99.

When asked why this device never came to be by TechRadar, Samsung isn't particularly definitive with its answer.

According to TechRadar, Samsung did create an aluminum mockup of a Galaxy Z Fold 5 with the integrated S Pen. It’s even possible to pop the stylus in and out of that slot. But this mockup is reportedly one of many Samsung created during the Z Fold 5’s development, and by the end it opted for a design virtually identical to the Z Fold 4 — albeit with the Flex Hinge that slimmed down the design and closed all gaps.

According to Samsung Head of MX Design Hubert Lee, Samsung didn’t offer a built-in S Pen because “there's a lot to consider. You can't just stick a pen in there. If you stick in a pen in there are other cost consequences. For now, we decided not to have the pen in the Fold." Samsung EVP and head of R+D office Won-Joon Choi later added that “every millimeter, every gram matters."

Neither of which are particularly definitive answers, and are open to speculation and interpretation.

The impact of the S Pen
Cost is an interesting one to think about considering the S Pen is only available as an optional accessory right now. A standard Fold Edition S Pen currently sells for $50 on Samsung’s website, while the more refined Z Fold 5 S Pen is $55.

Bundling that in with a Z Fold 5 would either eat into Samsung’s profit margins, or push up the price of the phone. Considering the Z Fold 5 sells for the same $1,799 price tag as the Pixel Fold, the latter would have given Google a sales advantage.

It’s unclear how much weight or thickness the S Pen could add to the Z Fold 5. From the sounds of things there’s a chance it would have pushed those numbers up, which isn't ideal if you’re hoping to market your phone as the thinnest foldable you’ve ever made. The Galaxy Z Fold 5 weighs 8.9 ounces, which is an improvement over the 9.2-ounce Galaxy Z Fold 4.

What Samsung didn’t mention is that making room for the S Pen inside the Z Fold 5 likely meant removing something else. Space inside a smartphone is at a premium, especially when you’re trying to make it as thin as possible, and every inch counts.

The battery life question

Definitely expected. Putting an S-Pen into a Foldable device. You will need to change the entirety of the current design...
Mega pricy and the S-Pen will make the device thicker for sure.
Battery capacity is often on the chopping block in these situations, and given the Galaxy Z Fold’s history of weak battery life, reducing the amount of available power compared to the Z Fold 4 doesn’t seem wise.

Our battery life testing saw the Z Fold 5 clock in a battery life of 10 hours and 55 minutes — 98 minutes higher than the Z Fold 4’s 9 hours 17 minutes. Which is better, but still a way off the 11 hours 30 minutes needed to score a place on our best phone battery life page. Had Samsung reduced the battery capacity to find space for the S Pen, that lead would have been severely diminished.

Redesigning the phone could have prevented such a thing from occurring, and this was something Samsung had considered. According to TechRadar, the Z Fold 5 went through a bunch of different prototypes, including some that altered the aspect ratio and would have made the phone more akin to the Pixel Fold.

As it happens, Samsung stuck with the same general design as the Z Fold 4 because they believe it’s the best for “usability and grip and portability." Though that is all down to personal preference, and we found during our testing for the Pixel Fold review that Google’s stockier foldable design was noticeably more comfortable to use with the cover display.

Despite its flaws, and relative similarities with the Z Fold 4, the Galaxy Z Fold 5 is still the best foldable phone out there. That’s all thanks to the improvements to battery life, multitasking and photography.

Source: Why doesn’t the Galaxy Z Fold 5 have a slot for the S Pen? Here's what Samsung says

Fold 4 vs Fold 5 vs S23U Camera: https://www.youtube.com/watch?v=wPq1zoA-zSw

Looks like Fold 5 is almost like S23U I feel. Could be = regular S23.