No one here can really know what records you need or don’t need. There are some seemingly obvious assumptions that one could make, but it it sounds like you already know to keep your MX record and anything else that GMail had you add.
If you cannot simply remove whatever WPEngine had you add, your best bet will be to go through your DNS and figure out what each record means. You can also back up your data with an export before you delete anything. That way you can quickly recover if you delete too much.
One long awaited new feature that finally arrived in the Cloudflare DNS app may prove helpful for you going forward. You can now add a note to each DNS record.
Hey thanks epic.network fo for your advice and for getting back. I didn’t know about the export feature, So I can just go down that route, and trial and error changes. I’m sure it’s going to be fine if I just cancel WP engine but it’s good to know I have everything backed up if I need it. Thanks again for your help