Mock-up Usage

Mock up usage?

Hello.

I want to present designs on an online site to be printed and framed (I think buyers mostly buy them for this reason). During the process of placing these designs on poster mockups, I have some concerns about mockups and I would like to consult you about them.

Should I definitely use mockups as a preview? Doesn't it make sense to put the design itself directly? Or, since the mockup is an artificial image, could it be misleading for the other person? This last statement confuses me a lot. In this regard, I am worried about the appearance of the design being pale or bright in different mockups. What should I think about this? I don't want a misleading situation to occur and I also want to be able to show the stance of the design. I don't have the ability to take a real photo. Can I use mockups with peace of mind? What do you think?

On the other hand, the mockups I can find usually contain one, three or five files. Is there a source with mockups containing many psd files? Can you tell me? (Sorry for the length of the question. )

I look forward to your comments. Thank you very much in advance.