The answer to this is unique to each family.
Some families, as mystic said, maintain the wives in separate homes. No problem.
Others all live under the same roof, but with separate rooms, and hubby rotates. PDAs (Public Displays of Affection) are based on that family's rules.
Other families sit down together and say, "We none of us got married to sleep alone". So they share one big bed in one bedroom. A bit hard to worry too awful much about what is visible or not in that situation.
Within that group, some say Yes or No to other things, or define appropriate places and times -- and some say anytime, anywhere.
Further, this may change over time. What seems to need boundaries, and raises concerns at the beginning may well diminish over time. Similarly, high hopes may be dashed on reality and it turn out that more limits are needed for one or another's sanity.
Finally, the definition of modesty varies. Some of us claim to have seen completely modest folks at nude resorts, and wildly immodest folks covered to neck, wrists, and ankle -- maintaining that modesty has more to do with the "old come hither" in the body language than the amount of yardage involved.
My best advice: Enjoy living. And seek another who enjoys living much as you do. As for your wife's concerns, perhaps if/as she comes to truly love both you AND her new sister wife, her concerns will ease, and she'll be as happy at seeing her be loved as in being loved herself.