The only reason to want non-RBF transactions, is to accept zero-confirmation transactions. But, with more and more full-RBF nodes, you shouldn't rely on that. Just wait for a confirmation to be sure.
Yes, exactly. In the past, I accept no confirmation transaction if the fee used is high enough to make the transaction get confirmed in the next block. But since nodes can enable full RBF and non RBF transactions can still be replaced, I do not do that anymore. At least I wait for one confirmation. I also see no reason why OP need transactions that is not supporting RBF.