I keep a month of expenses plus a small vacation reserve. Then I have an EF and separate savings brokerage I keep invested in SHY, which is a short term treasury fund yielding 2.7% last time I checked. I find the volatility acceptable in exchange for a yield that's slightly higher than HY savings or MM. In an emergency, it would take three days to sell and settle, so I would rely on my credit lines if I needed cash within three days.
I also think the 2.2% at Ally is a good choice. I've considered shifting some money there but never pulled the trigger.