Yes, you can install over 300 games: this was also true without a9lh (which, as already pointed out, isn't a factor) and even without cfw (if you had 290 original games then started adding legit cias...)
The issue is that Home won't display more than 300 icons (not only games: badges also count against this), but you could still use alternative launchers (FBI 1, 2, and DevMenu can run applications)
You can install >300 games using one nand, but you won't be able to see >300 games on the HOME Menu on that nand.
You can launch >300 games using apps like FBI, DevMenu, or freeShop.
You can install >300 games using one nand, but you won't be able to see >300 games on the HOME Menu on that nand.
You can launch >300 games using apps like FBI, DevMenu, or freeShop.