Spouse Visa 2.5yrs or 6months Confusion

I'm doing my research on appropriate Visa for my partner and i noticed this on HO website:

"You’ll get permission to stay for 2.5 years, or for 6 months if you’re applying as a fiancé, fiancée or proposed civil partner.

After this you’ll need to apply to extend your stay."

Does this mean after the 6months Visa (during that time we get married) for my fiancee, she can apply to extend in country? How much?

Will I pay the same Spouse Visa fee regardless of how much time she is given? If this is the case would I not be better off applying for a Marriage Visa first??

Does this mean after the 6months Visa (during that time we get married) for my fiancee, she can apply to extend in country? How much?

Yes. £1033 plus IHS of £1000 for a 2.5 year visa if you meet all the requirements.

Will I pay the same Spouse Visa fee regardless of how much time she is given?

A 6 months fiance visa is £1523. A spouse visa applied for outside the UK is also £1523 but you also pay IHS of £1200.

If this is the case would I not be better off applying for a Marriage Visa first??

Be careful, there are two different marriage visas
Once is about £80 and is a marriage visitor visa and you cannot switch to a spouse visa within the UK. The fiance visa is part of the settlement visa group and costs £1523 for a 6 months visa and has an English and financial requirement.