Hello everyone !
Umm, I don't really know how to start this. I am actually new here and I don't know all the rules so I am asking for pardon if I broke any rules. Thank you for considering
I currently have hard-tail mountain bike but road biking fascinates more so I want to start road biking. I’m planning on buying a bike from online shop. I went up on the internet to know my suitable frame size but the thing is, different sites are suggesting different bike sizes suitable for me. In some of them according to my height I should get a S(48-51cm) bike in some M((52-53cm). Now I’m really confused.

Basically my question is, what is the perfect frame size for me?
Stand-over height: 5’4”
Inseam length : 27” (inch)
Preferred riding style: Sportive

Thank you very very much
PS: I know the best solution is to go to a bike shop. But there’s some reason I can’t go to one. If you wanna know why you can ask me.