Funny how you picked a very similar looking set of modules to those in my “starter” rack:
I can relate to your questions. I considered the EricaSynths Pico DSP as a basic effects option and would’ve added it if I didn’t have the ability to run it through my Octatrack.
I would like to add Erbeverb, Phonogene, and Rainmaker to the setup, but that’s a whole rack right there.
Since you’re going for an ambient sound, perhaps get a good reverb first, so replace the Morphagene with an Erbeverb. Not that the Morphagene is bad, but it’s a grain pitch shifting sampler, which isn’t necessarily ambient focused. I think you might want to explore some additive synth options, such as the Audiospektri HG-16. You need a delay module, too.
Regarding filters, have you considered the uJove by System 80?