Applying to schools in the US - Theoretical fundamental physics I am a theoretical physics masters student, currently on the process of applying to universities. I find it incredibly hard to gauge which universities I'm most likely to be accepted in. All the professors I asked, suggested me the top universities in the US.

With my grades being a first class in my undergrad(standard for theory?), and my physics GREs being about 670(kinda bad..) I find it really unlikely for me to be accepted in these schools(Princeton, Harvard, etc.)

Since I already have taken modules in advanced theoretical subjects, that might give me extra credit, but I don't have much research experience(at least in theoretical physics).

What kind of schools would be a more suitable choice for me?
Acceptance to a doctoral program in the US requires a broadly positive background and evidence that  you will succeed in the program you apply to. It is unlikely to hinge on any single thing. But letters of recommendation are very important, especially if they come from established researchers, preferably well known. 

But the US has about 130 top research universities (R1). Some of them have larger programs and others are small. Relatively speaking Harvard and Princeton are small in any given discipline. State funded universities tend to be larger. 

No one can predict what will happen based on such limited information. I suggest that you apply to several places, some at the top, as you have been advised and some others that are still excellent. 

You can also do a bit of research on the places you might apply to. Figure out who is on the faculty and what their specialties are. Look at a paper or two from some of them to see if you are still interested. Note that a "top" university may not be "top" in every field. Look closely but cast a wide net.