Well Op 32 No 5 sounds and looks easy, but it isn't. It is neither fast not flashy, but those 5 v 4 and 5 v 3 rhythms are not easy, and you need to be able to play a very controlled pianissimo.
But the famous Prelude in C sharp minor Op 3 No 2 is the opposite of Op 32 No. 5 - it looks harder than it is!!
Relatively easy (for Rachmaninoff) are:
Barcarolle Op10 No 3. Rather long, but nothing horribly difficult in it
Melodie in E Minor Op 10 No 4
Moment Musical in D flat Op 16 No 5
There are no cross rhythms in the Melodie. The other two feature 3 v 2 rhythms which are easy to master, if you haven't done so already.
Some of the Etudes-Tableau are monstrously difficult, but Op 33 No 8 in G min is an exception, and a very beautiful piece when well played (unlistenable otherwise)