Old deck, will be prepping and staining. Reading a lot of different things and don't know which apply to our deck with regards to what we want to do. Seeking advice

Good day all!!

I'm reading so much about this that my head is spinning, there is so much information but I'm not sure what applies to what we are trying to do with what we have.

Deck:
*I believe it to be 15 years old. Unsure if it's been maintained, would think not. See pics here: (also attached: https://imgur.com/a/HwDuChN )

*The foundational pieces seem to be in good shape

*There are boards to remove, mostly on the top of the railing. I've read that once they are installed, we need to wait 3+ months.
*** Note: the lumber store (not big box store) I bought my top of railing from said that only a few days was needed after install. I did a waterdrop test by taking a regular straw and emptying it's contents (so a decent amount actually) on the board and within 10 minutes it was absorbed but not dry to the touch.

*I'm seeing that we need to put cleaner, stain remover, brightener on it as prep, then sand.

.... so here goes, I'd like some advice:

* We plan on using a pressure washer (2400 PSI, 25/30% nozzle) to strip the stain (it is stain right???( https://imgur.com/a/HwDuChN)) and then let it dry for a week.
* Then we'll find a stain that will be similar to this end result ( https://imgur.com/a/hiCFl6e or see attached railing color) and apply it to the whole deck. I'm assuming to achieve this type of coverage ( https://imgur.com/a/hiCFl6e or see rail color), we need to put a solid color stain/sealant, probably 2 coats.

* Do we really need a cleaner if we're using pressure washer?
* Do we really need to use a brightener if using solid color stain?
* Is sanding (I have an orbital) at 180-220 grit actually worth it for this older deck?
* Regarding the water drop test on the top railing boards I have which mentioned earlier in the post, since it absorbed and didn't pearl after 10 minutes, does that mean a few days is all I need after install before applying stain? Note: The deck boards for the floor, they did not absorb the water...
**** Is that just surface? How do we know the water drop test is still working for the middle of the wood?

So..Many questions, I'm sorry if this post is too long. Hopefully some advice related to what is written above can be given...

Thank you for reading!!