Not OP, but Slack/IRC/IM of some kind is the answer to most of your questions. I've bounced around between shared office, private office, cubicle, private bullpen, and open office my whole career, and by far the least productive I ever was was in the open office. In all other situations, my team communicated mostly over instant messaging, or if it was really important, by wandering down to their office and knocking.

Since most team communication happens over IM, it's easy for anyone to read back on what they missed. Most teams also do daily stand-ups or other meetings, to catch the larger group up on anything important.