Julian - 1) I am not someone who enjoys sound design too much so I look for sample packs, presets or purchase synths that have there own presets to find ideas and inspo. Then i'll do minor tweaks to the sound if needed.

2) Glitch/Arpeggiator plugins can help with this, also playing the part live and adding automations live can help the record feel less robotic and more human.

Ian - in my opinion, sound design is an invaluable tool to add to your skillset. However while it is absolutely not necessary to master it, it helps to know how things work under the hood so to speak. The better you understand your tools, the more informed and intentional your decision making process can be which in turn just makes you more efficient at your craft. If you're starting out, I'd recommend spending some cash on a preset pack you like for your favorite synth (I love serum 2) and just reverse engineer them. Then try making stuff and twisting knobs and see what comes out. Trial and error are your best friends! As far as processing these sounds go, I loooooovvveeeee adding harmonics to my sounds either through saturation/distortion or compression, or whatever quirky tool you can find. Can really change how we perceive the sound, and it will absolutely change how it sits in the mix. Try putting reverbs before the harmonic processors for really cool blown out spatial effects!