Welcome to the forum poopje.
Since text styles are all about the formatting of text, when you apply a style the formatting has to change. There's nothing you can do about it but you can make it work for you instead of fighting it.
What you need to do is create character styles and paragraph styles that are based on one another in a hierarchical way.
Consider the attached document. There are two character styles:
* Base Character Style, and
* Superscript Character Style Based On Base Character Style
and one paragraph style:
* Paragraph Style Based on Base Character Style
(Normally you would choose better names for the styles, these are just for explanation purposes.)
'Base Character Style' has the "normal" formatting that you want applied to the text: font; size; etc.
'Paragraph Style Based on Base Character Style' is based on 'Base Character Style' and can be applied to paragraphs or "whole frames" (which is actually a shortcut telling Scribus to apply the style to all of the paragraphs in the frame, you can't actually apply text formatting to a frame itself).
'Superscript Character Style Based On Base Character Style' is based on 'Base Character Style' but is set to use superscript instead of normal formatting.
(When you're making your own styles, make sure you're using the "Based On" field to "join" the styles.)
To format text, apply 'Paragraph Style Based on Base Character Style' to the paragraphs (frames) first. Then apply 'Superscript Character Style Based On Base Character Style' to the words that need to be superscript.
If you then want to change - for example - the font, then change it in 'Base Character Style'. Making the change in 'Base Character Style' means that every style that is based on that style will automatically change to use the new font.
If you create this type of style hierarchy it's very easy to change the formatting of the document later by changing the base character style. The change will ripple through all of the styles that have been based on it.
Try it in the attached document. Try changing the font in 'Base Character Style' from Arial to Times New Roman and see what happens. Then try changing it back again. Quick and simple.
Using styles like this is a tiny bit of extra work to set-up in the first place but the time you save when you want to change something can be huge. Imagine that you have hundreds of pages of text and you find out you need to change the font. Manually changing the formatting will probably mean that you have to go through the whole thing re-formatting for superscript etc. (if you can remember where the formatting should be applied). Re-formatting through the styles only takes a moment.
Styles can be a bit confusing at first but once you've got your head around them they work very nicely.