I think you will be fine with 32 spokes unless you are over 220lbs or packing serious weight.  The flow ex rims are plenty stiff.  I have built wheels using both hope hubs and shimano 26 and 29, all with 32h, never felt like more was necessary.  I weigh 180 and take up to 40lbs extra on the bike when fully loaded with H2O for bikepacking.  Currently on my bikepacking bike (Salsa El Mariachi) I have Flow Ex 32h 29" laced to red hope proII hubs with DT competition 2.0/1.8/2.0 double butted spokes.

Things to consider:

Hope hubs are nice and are a good deal when compared with other top-end hubs (king, etc.), but are still expensive.  Also they are loud which for me is only noticeable when I am pushing the bike around the house, and has never bothered me on the trail.   The freehubs are fully serviceable with 4 independent springs and pawls.  Even if one breaks on a ride (which has never happened to me) you would still make it out fine.  Bearings are replaceable cartridges: easy replacement in 4-5 yrs, no need to adjust bearing tension.  Also convertible to any type of axle.

Shimano hubs are cheap and (nearly) silent, but have durability/serviceability issues.  I run those on my beater/around town bike.  Personally I've never had a problem, but others have.  The freehub is not serviceable, replacements are ~$30.  I would recommend to get SLX or better yet XT, the differences are in the quality of the dust seals.  Bearings are loose ball bearings slathered in grease with cup/cone adjustment.  This takes some practice to get right, and some cone wrenches, but it's not hard once you get a feel for it.