Have sex in the same bed? No. Well, I have heard this once or twice, but I can't emphasise enough how extremely rare this is. Try to think of this from their point of view. It's a marriage, not a porno. :-p
As theories go it could be worse. On a defunct plural marriage site there was a guy who would tell all the woman he was trying to romance (frequently even the married ones)that the best way to go was for him to have the master bedroom and that whatever number of wives he would accumulate would all share a bed in the second bedroom when it was not their night with him. Also something about multiple sets of bunk beds in time.
Yeah buddy...sure thing. Let me know how that works out for you.
Everyone my wife and I have been in contact with are pretty clear where they stand on this issue. The ones we chat with want their own space within the home so that means own bedroom and bed lol. My wife also prefers it that way. Of course there will be times when that doesn't happen like when we all go camping. From a man's and husband perspective I'd advise you to simple ask if your unsure. I hope you find what you're looking for Sergeantforce. Our family thanks you for your service too.
I've seen polygyny practiced very successfully over multiple decades so I draw from those examples. Each wife needs her own 'space' in addition to the common areas. Otherwise there will be friction and that will lead to problems IMO.