I'll just tell you what I do. First, I don't use wheat. Of the options for pils malt, I'd go with the Bohemian, it'll work fine. I really think you'll get the yeast character you're looking for by going with WY2565 - it has the subtle white grape character that I think of in good kolsch. Other strains are more bland IMO. Personally, I don't step mash kolsch. A mash @ 150F for 75-90 mins works just fine IMO. I shoot for right around 23 IBU, added as FWH. I use Mittelfrueh or Hersbrucker. Sometimes I might or might not add a small amount (1 oz) of same near the end of boil. I cool to 60F, hold 62F for 3 days, then ramp a couple degrees/day to the upper 60s. 2 or 3 weeks of cold lagering is beneficial, as 2565 is slow to clear. I usually gelatin fine as well.
There you go. I'm sure other brewers might do it differently, but this makes a great beer.
I have a Kolsch in the keg right now that REFUSES to clear. I've dosed it twice with gelatin. I used 2565. Is this normal in your experience? It's ridiculous.
But yeah, I did a step mash on mine, same as I do with my lagers - 145F for 60 minutes, 160F for 60 minutes, 60 minute boil. I totally get the subtle white grape character with that yeast. It's good, but very annoyed it won't clear. It's been a couple weeks now.
And, I hope this wasn't a mistake, but I targeted 5.4 pH and added 3mL lactic acid to the kettle to bring the pH down. It doesn't take sour or anything in the keg, so... I probably should've just targeted 5.3 in the mash and left it alone after that.
I'd go with Bohemian pilsner malt, skip the wheat (don't know where this came from and why). Kolsch is a cousin to Munich Helles, slightly higher in IBU and with an ale yeast. No reason for the wheat. But who am I to argue with the Germans on that... I just don't see it as necessary.
I'd go with Hallertau at 60, or FWH with a bit and add a bit more at 60 minutes. Don't need to get too complex on the hop additions for this.