if you run your own domain and have a wildcard for email this is a very good strategy. I also never provide my real birthdate for (almost) anything. The vast majority DO NOT NEED IT, and the rare case where it might be required (still doubt it, but maybe age of majority or consent, or a waiver) I use Jan 1st of the real year. This has caused problems (ex: doesn't match your id) but on the balance seems to be positive.
Even without your own email hosting, Gmail kind of lets you do this by appending +whatever to your address before @gmail.com. Obviously this can be trivially detected and stripped but I suppose it is better than nothing. Multiple real Email addresses are definitely a best practice.
Like: myname+whatever@gmail.com?
Yep. I do this a lot. It occasionally doesn't work (eg: some sites don't think + is valid).
To be fair, I don't think it's made a huge difference in my life. In fact it's possibly been more of a negative than a positive.