The 408 doesn’t have a beta range per se, it has a ground fine setting. What you would probably consider a beta range is actually ‘hidden’ in the first few millimeters of the reverse range. (You can ‘tickle’ that spot to get the change in prop tone and then back into fine and the props will stay at that angle- this is all unpublished behavior/technique by the way) Now unlike the caravan, this thing at idle does want to go quite fast during taxi with the throttles at idle. At light weights if you put the condition levers to cold start you could probably break ground contact - at idle!
Some more technique gouge- you release the parking brake and throw the handles into fine as soon as there’s forward motion. For turns bring the outside prop up into idle to assist the slow steering bungie response, then back into fine. When the aircraft comes to a stop, during taxi or holding short or whatever, brakes are set and power levers go back up into idle to keep the air moving over the engine nacelles for cooling, to avoid throwing fod out in front of the props, etc.