Okay, I would think for what you plan on doing, the CP around NRT will do fine. Yes it is a tired Japanese CP so no design star or anything like that, but should be clean and overall functional for such a stay.

Hauling luggage wise, getting to the IC Strings, I dare say isn't much more work than making your way to the airport shuttle and such. Once you get to the NEX on NRT and then arrive in Shinagawa the main headache is navigating the station and making your way to the Central Gate and then turning right to Konan Gate and another right at Arte Building (Dean & Deluca) and walk 200m or so (all covered) and you are at the IC. We have rollaboards of 16-17kg and it is easy peasy, but we also know where to go and all that.

The IC is of course a way nicer hotel, but whether you need that this time around or not and rather save the points / free nights is really your call.