In addition to being a bit heavier, the Nimbus has a narrower rim. This increases the likelyhood of the tire folding over the rim on side hops (I don’t think it’s an issue for most) and the impact from drops and bumps isn’t dampened as much.
Most feel 165 cranks is too long on a 24 (~ half like them on the 26. I like the 170’s on my 24 Muni) and use 150’s. If you are good at climbing hills and have a brake for steep decents, you may preffer 137’s. I’d get the dual hole cranks (either 165/137 or 150/125). If UDC doesn’t have one or the other, they are likely temporarily out of stock.
Instead of hydraulic brakes you can set up v-brakes. Clearance is usually a problem for Muni tires, so you’d want them w/ the longest levers you can find (which is the main reson people run hydraulics, so they can easily run a 3" tire).
-Or you could get a Mountainuni disk conversion. (I have conserns that the disk would get damaged too easily in UPD’s or slice my leg, but I haven’t herd these issues as being a problem for the people who have them.) The braking is supposed to be more progressive than Maguras.