Stamp 5 timelines and approval queries

Hi All,
First time posting here so hopefully I am doing this correctly. I am thinking of applying for a Stamp 5. I have been here for 16 years on a Stamp 4. I do not plan on applying for naturalization. I know this used to be a very quick process, but it seems like it is taking a lot longer now. Anybody with experience that can advise on what the wait times are like? I was also wondering, do most people that are very straight-forward and fit the residency requirements get approved? Do they come back looking for additional docs? Is there a lot of hoops?

And in case anyone has done this recently I have a few other queries around documentation that I hope someone can help with:
1) Do I need to send all the pages of all of my passports or just the picture/ signature page plus the pages with stamps
2) Do I need to send in a P60 for every year I have been here? OR just the last 8?
3) If I can't find all of my P60's, would a P21 balancing statement be okay?
4) Since P60s are no longer issued for the last few years (2019?), I assume the Employment Detail Summary will be okay?
5) I am sure I've seen online somewhere that they also require bank statments, but I don't see it on the application. Is this accurate?
6) Do I need to provide a cover letter?
7) In the application there is a section to put additional details thatI think might be relevant. Do I need to put anything there?

Any more information about the process to make sure it goes off cleanly would be incredibly helpful. Thanks for taking the time to read this. I didn't think it was going to be so long!!!!