Just share my experience with you.
1. Those drop-in plugins should be related to your cache plugin, maybe w3 total cache? But it's normal. Why do you want to remove these 3 drop-in plugins?
2. That internal server error usually related to your hosting / server environment. Any clues when you started facing this internal server error? Then try to find out what changes before this problem occurs, could it be any setting changes on your web server setting like PHP, MYSQL, or maybe after installed certain plugins?
1. Those drop-in plugins should be related to your cache plugin, maybe w3 total cache? But it's normal. Why do you want to remove these 3 drop-in plugins?
2. That internal server error usually related to your hosting / server environment. Any clues when you started facing this internal server error? Then try to find out what changes before this problem occurs, could it be any setting changes on your web server setting like PHP, MYSQL, or maybe after installed certain plugins?