Personally, I'd go for the CIC or CIU now and get the clock started until your next Chase biz application ~3 months from now. With some uncertainty how much longer the elevated 50k UR offers will be around, I'd get them while the gettin's good. You're 3/24, with the oldest card dropping off in ~5 months. 2 slots is plenty to keep you busy for 5 months, especially if you're going for Chase's biz cards which don't add to the count.
Unless you have a need for the Platinum now, I wouldn't go messing around with trying to pull the 100k MR offer until probably the end of the year (and try to time it for an airline credit triple dip), because if you pull the offer then you really should put in an application right then and there. I know you've got plans to fly to Japan, and LAS has a Centurion Lounge. When's your trip, and do you have any other flights coming up when you can take advantage of the lounge?