Much depends on where you mainly ride and your weight really. I've just swapped over from Stans Crest 29er to Arch EX 29er, because like yourself I don't like feeling wheels flex.
Deepnding on season and how much kit I'm taking, I'm between 90 to 95kg in full riding gear. TBH, I've used the Crest 29ers for some pretty aggressive riding in Dalby and not noticed any flex in them. Also done some flying laps around Sherwood Pines on bits of the red and the latest XC course and not noticed flex, even when really flicking the bike over between corners and on the (albeit relatively easy) DH track.
Only time I really noticed flex was on some of the harder & rockier 'Dark Peak' natural trails, but then I was on a stiff hardtail, trying to stay in touch with a pal who does a bit of racing - and she was on her 140mm full sus!
I've only ridden the Arch EX wheels twice so far, but they are noticeably stiffer. I'm using them on my full-sus 29er - not sure if they'd feel a little harsh on a hardtail, but of course, it depends on the frame you've got.
IMO, if you're less than 80kg in full kit and don't live somewhere where there's a lot of loose rock etc., I don't think you'd have any issues with Crests.
p.s. I have the AC MTB26 Tubeless on my XC race bike and they're about as flexy as Crest 26ers. Nice & light tho.