Learn Spanish (Latin America): Deberías personalizar el aspecto a lo retro. - You should customize the appearance in a retro style.

The phrase a lo retro acts as an adverb describing how the action (personalizar) should be done. The formula a lo + [adjective or noun] is a very common way in Spanish to say "in the style of" or "like." Here, it translates to "in a retro style."

What is the difference between using a lo retro and just saying el aspecto retro?

If you said personalizar el aspecto retro, you would be saying "customize the retro appearance" (implying the appearance is already retro). By using a lo retro, you are changing it into an adverbial phrase, meaning "customize the appearance in a retro style" (implying you are adding the retro style to the design).

Why use the conditional deberías instead of the present tense debes?

Using the conditional deberías ("you should") softens the statement, turning it into a piece of advice, a recommendation, or a polite suggestion. If you used the present tense debes ("you must"), it would sound much stronger, like a strict command or an obligation.

Does aspecto always translate to "appearance" or "look"?