Spoke count and larger riders.....

Stick with the 24 count rear wheel.  Very little aero loss and weight gain over 20 count wheels but a lot more stiffer.   You can even add a disc cover to make the rear wheel faster.

I have a set of Reynolds solitude wheels I use for training 20/24 spokes and I flux between 200 and 210.  Zero issues.

My mavic gp4's w/ 32 hole hubs are down right chunky but they have taken 30 ish years of abuse.     A good set of training wheels are nice to have.

I have that setup: Wheelbuilder bladed spoke Kinlin 300's with Powertap 20 front/24 rear on my roadbike.  I currently weigh 182. They have been rock solid.  They are stiffer than the 808's on my tri bike.

It's not as simple as "more spokes for heavier rider". A punchy rider tend to torque the spokes more, even if you are lighter compared to a heavier, but smoother rider. Then add road conditions, terrain, how technical the courses are, etc. and you can have vastly different results.

PowerTap hubs actually makes for a very sturdy wheel build. They have to be laced 2x on both drive side and non-drive side and the spacing is fairly wide, making for a sturdy platform to start the build from.

Then add the spokes themselves to the equation... certain spokes are just stronger then another spokes... Personal favorite is Sapim CX-Ray, strong enough for Belgian cobbles, but light enough to build a really nice climbing wheel set...

Long story short, you can't correlate # of spokes and your weight to how strong the wheels will be... However, if wheelbuild.com recommends you to go with a higher count, then I would go with a higher count... they really do know their stuff.