Going wireless with Skype for Business WITHOUT a dongle?

You are correct that Bluetooth has a relatively low bit-rate for audio. However, that is not specific to lap-tops. The bit-rate will be the same whether the device is a lap top or a phone. There is an enhanced bit rate option but it requires a chip from a specific manufacturer and it is not particularly widely implemented. Some of these dongles may implement it or they may not use Bluetooth at all. Ultimately, if the audio quality is subjectively ok for your application it will work.  Given that a wired headset is a pretty cheap device, the best solution is probably using the computer's internal Bluetooth for convenience and general situations, with a wired headset for when there is a situation when the requirement for audio quality trumps convenience.  If I was settling down for a 2 hour teleconference with clients  I would use wired.  If I am going to make a few quick calls with colleagues while generally doing other stuff around the office I would use Bluetooth.  Unfortunately, I as i understand it, Bluetooth 5 does nothing to improve audio quality - but I am not 100 % certain about that.