Suspension component advice needed

[Mr Flat Six]

Hey guys, I finally have some spare change to throw at my suspension on my 1999 Boxster with 89k miles. First the rear struts are worn and second I want more performance. I was going to order a set of Bilstein PSS9 coilovers. I mostly use the car for spirited mountain drives and have not yet tracked it but would one day like to do a track day to learn the car more. I've searched a lot but some of my questions are a little specific so its hard finding an answer. Hopefully someone here can help me out a little.

Since I am installing coilovers, should I replace any of the components that attach the suspension to the car? Specifically stuff like strut top mounts? Should I wait and see what they look like before hand? What has everyone elses experience been? Are there any bushings that anybody recommends to be replaced? I mainly ask this so that the car isn't sitting on jack stands for too long while I'm ordering and waiting for parts. I have also heard you need adjustable rear toe control arms when lowering a car or it can't be aligned as well. I'm not looking to slam the car and was wondering at what point of drop are these recommended? How low can I go without needing these?

I plan on eventually adding adjustable sway bars and end links in the future and was wondering how much more performance the adjustable sway bars and end links provide when being paired with the PSS9's. Part of me wants to do it all at once but it can get costly doing that. I do understand its to help fine tune handling. Lastly, when I go to install the coilovers, is there anything I should do specifically? I remember seeing somewhere to make sure you have them set equal or something before installing to make the shops job easier as far as alignment and corner balancing. The less I have to pay the shop, the happier I'll be!

Hopefully, I didn't miss something in all my searching and perhaps these questions have been answered. I believe I've found some of the answers to my questions in the past but can't seem to locate the threads anymore.