TEXTURE_BANDWIDTH_MULT under [Display] section of fsx.CFG controls video hardware’s texture transfer rate.
Default value is 40.
If a graphics card comes with 1GB or even 2GB video memory, you may try increasing the value for a smoother display quality.
My current setting is TEXTURE_BANDWIDTH_MULT=400 for Orbx’s NA and AU scenery addons; and 800 for default and general scenery.
Each hardware system is unique, you have to test it out for what works best for you.