Your issues are related to the number of plugins being loaded.

I primarily write Java in my professional life, using IntelliJ Ultimate Edition. I have to do so on a MacBook Pro with SSD to be productive.

Lately I primarily write Go in my personal life. I use the free IntelliJ Community Edition (with Go plugin only) on all my devices. On a CHROMEBOOK with 2 GB of RAM running Crouton, my experience with Community Edition is almost as snappy as my 16 GB MacBook experience with Ultimate Edition.

You can radically speed up your IntelliJ environment by being more judicious in which plugins you enable. Quite honestly, lately I've wondered why I bother with Ultimate Edition at all... since the only non-free plugins I really use are for HTML and JavaScript support (and even those only rarely). If my company wants to pay for an Ultimate license and a MacBook on which to run it, then I'll gladly use them... but if it were my money I'd probably just stick to Community Edition for my needs.