As a general rule, each additional UTXO you consolidate will decrease your privacy by some marginal amount. It's hard to give precise guidance since the observation model is different for whales vs small users and different for coordinators with large liquidity vs small liquidity.

If you start with only a single UTXO, there's a special case that triggers called Safety Coinjoins that will perform an extra remix for all of the outputs created in the initial round.

You can go to the wallet settings button from the ". . ." menu in the top right and check the coinjoin tab. Here you can increase the "Anonymity Score Target" number if you want to reduce your privacy progress below 100% again to participate in more transactions.