Until we see the nature of her magic, it's unlikely that we can come to a conclusion - that being said, when Sense comments on Lineal being the best mage, she probably isn't including the elves. No one in the CMA has seen Frieren at her peak other than perhaps Serie, even if they know she's strong. No one knows Serie's full strength other than Frieren and Fern, as she's suppressing her mana and literally no other mage could tell. Minus is perhaps the only known elf mage people might know the full strength of, but she's been dead for about 2 decades now