My tax preparer wants to file my taxes as cash basis. Is that ok? How does that compare to the accounting in Pocket?

The Pocket platform is set up for Accrual Basis, for the following business reason.

For business purposes i.e. if you want to get a loan or other alternative financing, provide financials for investors, etc, they will want accrual-based books, which is in accordance with GAAP (Generally Accepted Accounting Principles). However, it's not uncommon for books to be accrual basis and taxes to be cash basis.

This requires the tax preparer to do accrual to cash adjustments for tax purposes. 

Here's a helpful article that discusses How to convert accrual basis to cash basis accounting for your reference.