High storage usage with Samsung Galaxy S8 and image / image quality retention

My Samsung Galaxy S8 alerted me that the storage was critically full and may result in data corruption or failure to boot. I immediately deleted some apps to free up 2GB. But I am worried that it may have taken steps without my knowledge, such as clearing / disabling recently deleted (an issue as my screen was bugging and may have deleted by ghost touch without me knowing) or automatic lossy compression (an issue as I require some images to not have any compression artefacts). I am also concerned that the 2GB free may be a result of these optimisations, or whether it is a reasonably consequence of the handful of apps I deleted, plus the alert being given when there was already some storage free. I have two main questions: 1. are either of those issues likely? 2. how can I check whether these optimisations have been implemented?