I have been using ALLY BANK for ACH transactions, because they have BOTH a fairly good savings rate (2.2% at the moment), and work well for LARGE ACH transactions. Time can be an issue because I sometimes get next day completion, and on others, up to three business days.
I see HSBC is another options with large limits, good savings rates, but they also can be slow (2-3 business days).
Alliant CU has some limitations both in savings rate, and dollar limits.
Schwab is good on ACH size, but savings rate is currently lacking.
I see Synchrony Bank has good amounts, but no direct experience here.
Any other suggestions for find an ACH hub that has BOTH a good savings rate, and ACH size limits, and also has good turn around time on the ACH??
FYI - savings rates need to be consistent. Does not do much good to use them as a HUB, just to see their savings rate drop off over time. ALLY is not the highest, but has remained in the top tier for a long time.