How to pay vendors and receive payments from customers the cheapest and fastest way possible

You should explore MP. Some benefits are

* Pay a vendor invoice with a bank transfer or ACH transfer for free.
* Stretch your clients’ cash flow by creating up to a 45-day float by paying bills via a credit card, even if the vendor doesn’t accept credit cards.
* Vendors get paid with a physical check or with electronic bank transfers. You choose how you pay.
* 2-way sync with QuickBooks Online (data flows both ways).
* The setup of multiple users and approval workflows.

https:// melio.grsm.io/quickbooks

If you deal with multi currency transactions, we may recommend another options

Pay the vendors with ACH, directly from your bank account.  It's fast and easy.  

I don't and won't use Bill.com.  Research it here, in the forums.  Make that decision for yourself.  

So Paying via ACH or Bank Transfer...Is there a Charge for that?

There isn't for us, and usually isn't, But check with your financial institution to be sure. 

Thank you !    I will.