With the 301, everything is up to the person doing the virtual patching. For instance, with granular, itās easy to set an external offset knob to control the amount of randomness introduced to the selection of each new grain. But you have to patch it yourself (for this, Iād select the Start parameter of the granular unit, insert a S&H feeding random numbers to the Start parameter, and then have the range of the S&H controlled with a VCA āunitā within the 301, controlled by the external, physical offset knob).
Itās possible to build very refined units and to save them for later recall, or to use those that others have used.
To answer the specific Clouds question: The fabulous @rbeny built Ultraviolet, which is basically Clouds within 301. But unless you take the time to map the parameters of a given unit to external offset knobs or other controls, it wonāt be very tactile. For me, the main draw of dedicated units over doing it in the 301 is the tactility and purpose-built control scheme, complete with labeling. Also, I wouldnāt try and emulate characterful analog modules, because itāll be a compromise. My thinking is that I just patch and experiment with the 301, and once I start āreachingā for a given unit/function within the 301 all the time, I might as well buy it as a dedicated module.
There are also things that seem like they could only reasonable exist within the 301 ā for instance, user Mudlogger on the O|D site has done a fantastic collection of small units that bleep, belch, scream and tick ā random or semi-random. You wonāt find such a collection in module format, or at least it would get big, expensive and crazy 
Concerning reverb and delay: Thereās Freeverb on the unit, which is passable ā I wouldnāt buy a 301 for the reverb. Then thereās a bunch of delay units, which allow for crazy flexibility, but again, you need to build it yourself or use those others have built. Thereās Trash Tape, a really really nice lo-fi delay built by @scttcmpbll , so youāre not forced to do it from scratch.
