Unfortunately that's the nature of eChecks. They are the slowest form of payment and a merchant or seller won't ship until the funds are cleared which can take 7 to 10 days. We been in the online business longer than most, we don't ship until we have the money.
As that was your only option, you did what you had to do. Using PayPal is a learning experience. Had you had sufficient funds in your PayPal Account Balance, the transaction would have been paid for almost right away. Also, if you had a credit card, that would have worked too.
Even if you used your bank account, it can take up to 4 days for the funds to be transferred to the seller or merchant. Yes, as with an eCheck, the funds have been requested to leave your account however, there's a 3rd party system between your account and the bank which actually does the electronic money transfer. This is where time is lost as the transactions are run in batches.
Another way to pay almost right away is to do an Instant Transfer. In order to do this, you must have a bank account and credit card linked and confirmed.
The method that works best is to have sufficient funds in your PayPal Account Balance. This does take some planning ahead time but, is the best method as the merchant or seller is paid almost right away.
