Hi @shaun
Glad that you liked the plugin!
Yes of course, you can use your own custom contract. Look into their documentation about it.
Yes, we are working on a few ways to improve the plugin in a way that all new minted NFTs would be instantly visible on OpenSea (currently they appear after some time)
Also, keep in mind that the lazy minted ones will not be visible until they will be minted on the blockchain.