You should try and test a lot of things. But know that Pmax, specifically, tends to run on your brand keywords to lower the conversion price. So I wouldn't recommend it unless you have a representative that can exclude them for you, or if your brand name doesn't have much search volume.
ROAS is a bidding strategy while Pmax is a type of campaign so I don't understand why you put them against each other in such a way.
You can start testing different bidding strategies by either running an experiment (on the experiment tab) or by duplicating the campaigns and changing the bidding strategy. Unlike common belief, you can't really "compete with yourself", and you should ignore people who tell you that you can.
This is a great example for a campaign that can benefit from testing more competitive bidding or a different bidding strategy. If your bids are so low, you are running on keywords no one else is bidding on. They don't bid on them for a reason.
Last thing, if you want to quote multiple replies, use the
multi-quote function instead of replying to each on a separate message.