I'm a Taurus sun too, and I was also supposed to have Sagittarius rising but I didn't really feel like it fit (even though I was hoping it would
) either. So I'd like to ask: how sure are you of your birth time? Since (even with my certificate time) the chart didn't fit me, I'm getting a rectification. If you're curious at all about that, there are a number of people on this forum who are way more knowledgeable about how rectifications work.
I'm pretty new to astrology so please take my interpretation of the way the Ascendent works with some reserve.
One way to look at the difference between the Sun and the Ascendant can come down to how people perceive you. If you get the impression that strangers or people you're merely acquainted with regard you as different from the way that you feel deep inside, then you might have different Ascendant and Sun signs. However, it's totally possible for the signs to be the same, in which case you might feel very comfortable with in-depth (not cliche) descriptions of Taurus. And you might also have really good self-understanding since the "inside" and "outside" match, so to speak.
If you've been researching the descriptions of planet expressions in houses other than the ones your current chart shows, I would encourage you to keep open to the possibility that certain aspects in your chart might also (or better) account for your impressions of the validity of a planet's placement. As such, maybe you could consider starting off by looking more at the ascendent sign descriptions themselves to see what sounds more like the way you present yourself to others or how people tend to read you when they don't know you very well.
I hope this helps a bit.