I've use the Surface Ergonomic keyboard as my daily driver, and agree it is great. My only complaint is the indicator lights on Caps and Fn are not bright enough.

If you really want a dongle the previous Sculpt Ergonomic has a dongle but the Num Pad is separate :-/ It doesn't have the delay you talk about, and has much better battery life than the Surface version (had it for three years and have't changed them yet).

https://www.microsoft.com/accessories/en-us/products/keyboar...