She should fight as a witcher. We have always been told that Witcher training is so intense that you will always be known by other witchers; you are one of them just by the way you walk. Said by the White Wolf himself. She may be faster? Ok, she may be stronger, can be explained by the elder blood. A thing I wonder, maybe because of her elder and evil blood and now witcher mutations, she could be living for a long, long time. Last news about Geral being way younger as we thought was a bummer, I hope he'll be at least 120 yo and Vesemir maybe 180 yo.
You need to see both. Both are done very well. When they made FMAB they took for granted this was for those that loves FMA and want to see the real cannon ending. Watching FMAB they used information you know because you watched FMA and they didn't want to tell the same story again so they took for granted you know and will follow the script because you saw FMA. Simple both are good. To watch FMAB need to first watch FMA.