All PORs require a valuation to be approved. At the very least, the plan must provide for a liquidation value to ensure that impaired creditors are getting at least what they would get in a liquidation (e.g. Ch 7). This is called the “best interest” test.
If the plan is appropriating equity value to a class of creditors, then you also need to value equity to determine the portion of equity allocated to the individual classes (presumably pro rata to all claims/interests settled with equity). At the very least, the estate needs an equity valuation to determine the amount of discharged debt (i.e. claims not covered by equity value); discharged debt determines potential tax liabilities resulting from cancelation of debt (COD) income.
Valuation is a loose concept where the court typically looks for a DCF valuation. You may or may not need market valuations from comp cos/transactions depending on the industry/judge/counterparty to the valuation.
If all voting classes agree to the figures, then you can get away with less valuation support than in a more contentious situation. A non-voting class that feels that it's being wronged by a valuation should organize, approach the bench, and demand more objective proof that they are out of the money.