Do journal editors check self-citations? If I cite two of my papers, would it be a problem?
You have to expect or assume that journal editors read or at least scan any paper that comes across their desk. So they may also see what's being cited and what is not.
Now, it seems to me that you're worried about citing your own papers. There is, in itself, nothing wrong with citing your own papers: Oftentimes you're building on previous work you reported on previously, and citing your own previous papers allows others to follow your path of exploration. So these citations are ok.
On the other hand, it is problematic if you cite your previous papers because you want to rack up your citation count of H index. This would generally mean that you cite your own papers even though they have nothing to do with the current paper. Don't do that -- it's academically dishonest to do that, generally frowned upon, and may lead to your papers being rejected.
So the question for you to answer is this: If you want to add a citation to one of your previous papers, are you adding it because (1) you think it is a useful reference for your readers, or because (2) you want to increase your citation count? If the honest answer to the question is (1), then you should be on the safe side.