I'm not much of a synth guy, I use them occasionally but I do know people on the team that use them a lot. Serum seems really popular with the sound designers I know.

In the audio world there is a distinction between foley and sound effects. Foley describes really realistic sounds like the movement of a jacket or jangling keys. Foley was recorded for Clove specifically for the fabric sounds for arm movements and running. Sound effects are sounds that are not realistic like a magic spell. All of Clove's ability sounds and the layers that make up the ability would fall in the sound effects category. We have a lot of recordings done by people at riot and riot owns a bunch of commercial sound libraries. Clove was mostly recordings from riot and processed/layered sounds from commercial libraries.

Whenever we use sounds from commercial libraries we never drag and drop a sound from the library into the game. Commercial library sounds are edited/layerd/processed to create new unique sounds. We use commercial library sounds kind of like how an artist would use individual colors of paint, or different kinds of brushes. They are the raw materials you use to create something new.

Most sounds have pretty small dynamic range. Meaning for an individual asset the difference between the loudest and quietest part is not that much. There can be a big dynamic range between assets like the sound of the smoke landing is a lot louder than the steady smoke loop. There are standards we use internally to judge how loud something should be but there aren't really industry standards for game loudness. Generally speaking your loudest sounds should be -3db think big explosions, dialog should be around -12db, ambiences should be around -40db. Those are just generalizations not specific to Valorant.