Learn Spanish (Latin America): Ahora disfruto lo nítido de mi visión.

Both are completely natural! Using the neuter article lo plus a masculine singular adjective (like nítido) is a very common trick in Spanish to create an abstract concept on the fly. It means the exact same thing as la nitidez but often sounds a bit more descriptive or conversational.

Since visión is feminine, shouldn't the adjective match it and be lo nítida?

No, and this is a common trap! When you use lo to turn an adjective into an abstract noun, the adjective must be in its masculine singular form. Lo nítido acts as its own independent noun phrase meaning "the sharpness". It isn't acting as a descriptive adjective for the feminine word visión; rather, it's connected to it by the preposition de.

Can lo nítido de mi visión also be translated as "how sharp my vision is"?

Absolutely. The structure lo + [adjective] + de is incredibly versatile. Depending on the flow of the English sentence, you can translate it as "the sharpness of...", "how sharp the... is", or even "the sharp aspect of...".

I've sometimes seen disfrutar de. Could I say disfruto de lo nítido here?