You'll probably find lots of information about how to run a press release campaign if you write a good Google string (like for instance “how to run a press release campaign” or “what pitfalls to watch for in a press release”.

tictac2018 said:
I am reading online that it's preferred to paste the press release in the text of the e-mail but I also read that you are supposed to personalize your e-mails to press … this is very confusing to me.

Not confusing. Just don't send an email to more than one recipient, and in each solitary email, use the recipient's name and publication in the body of the email (before the pasted release itself). If you want to personalize even more, say you enjoyed the recipient's review of [some game the recipient reviewed]. Use some kind of visible sign differentiating email body from press release, like ### or “begin press release” / “end press release”.

Dear Bob, since your review of Game X, I think you would enjoy reviewing Game Y.

[tictac's real name], Game Developer Extraordinaire and future God Of Game Devs

Begin press release:

Press release goes here

End press release

I don't know. I'm not a marketing person. Use your creative sense and your best judgment. But I think reading “a few paragraphs” beyond the press release (which is also at least a few paragraphs) is a lot to ask of someone receiving an email from a stranger.