Re: which suspension set-up would you recommend and why?
another point to note is cost, height adjustable + damping adjustment coilover is range from low 2K to high 3K. lowering spring + aftermarket shock would be within 1.5K to 2K+. you get for what you pay for no more no less.
Since you're eibach spring, don't waste it. Just get Koni FSD or Bilstein B8 for shock replacement.
Try look into options like KW V1, is a coilover with only height adjustment. damping is fix by manufacturer. Or similar product from Bilstein, BILSTEIN B14® PSS
I'm on BILSTEIN B16® PSS9, I liked the height, handling & ride comfort. My man intention to change to coliover system, is I want that adjustability on the heights in order to achieve the ride profile I want. Personally, the ride is so much better after I put in the coilover system. Out of the box, BMW stock handling & ride comfort is very good. but till I ride on coilover setup I can't belive there is another level to that firmness, yet comfort wise is not compromise (of course comfort level is vary from drivers) . First, I set to 9' all round (softest, 1 is the hardest) at the installation and the height right, as how I want to the profile of the car. I keep a 10mm difference between height for front and rear, measure from wheel arch to low base of your wheel (not tire). I got this height different when I measure my stock height before putting in the coilover. After some 2 1/2 months running-in with more than 10,000KM clock on the system, I've request J4C to set to 5' all round. the ride is still not harder but dam very de firm. is not just good on corners, on high speed (say 90-100KMH) shift lane it very stable, zero body roll. all and all, I'm glad I choose coilovers.
good luck on your choice of upgrades.
coilover FTW.