PhpStorm remotely with XServer

I'm running PHPStorm remotely on an Ubuntu 16.04 machine through a client X server on WIndows 10. I'm using MobaXterm as the client X server.

The ping latency to my PHPStorm server is around 40ms.

Generally the speed is acceptable, but I am curious if settings can improve the following behaviour: Nearly all popup and dropdown windows have a delay of about 1s: Commit dialog, Ctrl-E, File Dropdown. However curiously Ctrl-Alt-F find files is much faster.

My remote server is on Amazon with plenty of CPU and RAM and I'm happy to experiment with settings.

Any thoughts on how speed can be improved?