Being tentative by using words like these can be polite.
All of your examples are similarly polite.
At some point tentativeness starts seeming a parody of politeness, or even "passive aggressive".
If you are being politely tentative, you should be happy for the person to say "no". If you are using tentative language to try to manipulate someone then you are being passive aggressive. But only you know if you are really asking if something is possible, or if you would be upset if the person says its not possible.
Among polite people, the default assumption is usually that the other person is being polite, especially in the case of a non-native speaker, so that a request not phrased as an order will usually be received without offence.