EQ, volume levels and compression.

Kapt.Krunch

Could you be a bit more specific please? I tried boosting aroung 5000 Hz and cutting around 150 Hz for bass guitar. And I'm not great with compression, just used a bass guitar preset. Thanks!

Just a thought but are those guitars properly set up.
string hight/radius/nut/fret levels,ect.
The notes on my guitars and bass are even throughout volume wise.
Also should be able to adjust the pick-ups.

Compression will make the dynamics more even (make the notes more even in volume). But you will need to play with the low end eq because it will also make the bass more boomy. 5000kHz is just fret noise. I wouldn't boost up there.
There is no specific setting. You have to use your ears.

Sam, are you using any heavy distortion on your guitar? Are you micing the cab, DI, using an amp simulator?

With heavy distortion, you'll find it to be a lot more "muddy" and lose clarity, which for an Electric guitar, means your high notes will scream, but your bass notes will lose definition.

If that's not the case, I'd look to a compressor first thing. The compressor will take your quieter notes and make them louder, while take your louder phrases and making them a bit quieter. Don't overdue it or you'll get a weird pumping sound (which can actually sound cool depending on the circumstances).