Same here, updated to 1.8.6 yesterday and there's now a huge delay on brush based tools, no less than 3 seconds before I start seeing the changes being applied, it is unbearable. I also noticed that working with he clone brush tool, it gets way too slow--almost unusable-- when selecting "current layer & below" but its performance drastically improves when working only with "current layer" and this option is relevant to my line of work for a non invasive editing. again, this issue only became apparent after the update. Currently running an iMac with Mac OS Catalina, 32 gb RAM, 2 TB HDD, 2 GB radeon for graphics.