I used to have a NCase M1 with 9700K and the same motherboard.
If you use air cooling, 9700K - 9900K + Prime95 Small FFTs @ 99C is quite normal.
Neither Noctua NH-C14/S / BeQuiet Dark Rock TF (the best top-flow air coolers for M1) nor Thermalright Silver Arrow 130 (the best side-flow air cooler...