OPL was designed to not require the DNAS/IOP patching anymore. For best results, you should use plain raw untouched rip of your game.
But, that doesn't mean they won't work with OPL, you should try. However if they already work in ul format, they will too in ISO.
As said, there is really no difference between two format in terms of compatibility.
PS: for your question on conversion, see my post above, I edited it after reading your post
It's too late to think that we can worship human emotions
Because we've already evolved into machines in our minds