Is RAM capacity or speed more important for office work?

RAM capacity is far more important than speed for office work. Running out of memory causes swapping, which kills performance far more than the difference between 3200MHz and 3600MHz. 16GB of slower RAM will feel better than 8GB of faster RAM for spreadsheets, docs, and browser tabs. Get enough capacity first (16GB is the sweet spot), then consider speed only if the price difference is tiny.