The voice is not important, IF you're unclockable as far as visual presentation goes, cisgender looking in every aspect, even when you have messy hair and are too lazy for make-up... There are many cisgender women with really low voice, and other than problems with telephone, they are not getting misgendered or read as transsexual because of it. The more visual masculine traits you have, like facial features, height, shoulders, hair, lack of hips, lack of breast size, etc... that much more likely is that your voice will be THAT THING that would get you clocked. You can try to hide masculine facial features with make-up, and masculine body caracteristics with appropriate clothing choices, but in the end, no-matter the effort, those things are still evident to some level, and with voice that isn't enough feminine, people will start searching and looking for clues.
If you plan to live stealth in the future, definitely start to develop your voice, or start saving for surgery. "She has a deep voice, but I like it" will probably work with most men. But it's enough that one woman get suspicious and start looking for other clues... And your life as you knew it, could get ruined and destroyed very fast.
