.. a bit confusing, but I think you are saying ...
I'm applying for a fiance visa..... and if it gets refused, while I appeal, can I also apply for a visitor's visa ...
.... if that is what you are asking/wondering ..
I would say NO.
The fiance visa is the "easiest" one to obtain.... because u are supposedly going to get married & live in
happy wedded bliss the rest of your lives.
If the Embassy does not believe this (ie rejects the application) .... I cannot see them issuing a visitor's visa
.... as they've already rejected the premis that you are a "genuine" couple.
... only my thoughts ... but ....