How to choose a masternode, where to find them?
You can use this service to review active masternodes in the test network: https://monsternode.net/validators.php
You can choose one or more of them, the revenue is determined by the percentage of your coins in the total stake, so you can choose any one you like, the rewards will be the same.
When choosing, you should also pay attention to the team, the support level, and the community of the masternode. Please also read the terms and conditions offered by the masternode owner and analyze its statistics, and, more importantly, the level of technical support.