I´m able to correlate that Finder is becoming unresponsive ~1min into any command while Safe boot works fine. It is definitely a GPU issue. I´m running MBPro mid 2015 with full power, clean install 10.13.4 and the only way to interact with the system is to use Path Finder to force Finder to quit at login. Every app and pref pane that requires interaction with the builtin finders browser becomes unresponsive for ~3-5 mins, sometimes completely. It helps to disconnect externals USB drives, but as my work largely depends on external storage, macOS becomes quite useless.
TLDR = Try Path Finder and tell it to quit finder and PF creates it´s on desktop. I´m currently running PF8 (beta) and it´s very fast, but some minor glitches and update from day to day. It crushes Finders performance though and it seems like my laptop is allergic to anything Finder related right now.
- oh yeah... My fans are completely bipolar. I can literally track the sound of a software iteration loop and thus far, the only solution has been to boot into safe mode, followed by normal. Safe boot works very well and is sort of what Im resorting to in the meantime. The fans are either SUPER SPINNING or quiet.