I have owned a Behmor 1600+ and I can say that overall I was never too impressed with it. It is definitely a "low (heat) and slow (time)" type of roasting machine, the profiles aren't ever geared toward "hot and fast" roasts just different lengths of time with a limited heat spectrum. I always used manual mode anyway and tried to get more heat out of it by using some hacks I found on the net but overall it always seemed underpowered. The heat factor plus other things are really important to produce those flavors in the coffee you are seeking. I upgraded to a propane heated, drum roaster that allows for roast profiling as well. Many of the users on here are using similar machines (gas powered, drum style) and the results I can say are noticeably better.
I cannot say that the Behmor was a total waste though. I learned some good things with it and they are easy to sell but overall if you are wanting to have a large window of flexibility to apply different roasting techniques to a coffee then something with more versatility and heat output will be necessary. Your produced "volume" in the cup with the Behmor can't go higher at this point
Also, I don't think you can use profiling software with a Behmor w/o some tricky mods being implemented. I never tried to find out much on that topic though, maybe others on here have more insight into it.
Lastly, in reference to you 3 observed areas of improvement, they didn't seem super specific so I will give general feedback.
1) Bean quality sets the ceiling of possibilities in the end "flavors" resulting in a cup/espresso etc. 80-100 pts.= specialty grade coffee, within that spectrum you have lower and higher ceilings of flavor possibilities which are also origin dependent, 80 pts. being the lowest ceiling, 100 pts. being a mythical creature who only dwells in the jungles of Wakanda. Choosing beans is very contextual but learning to roast with lower quality specialty grade beans is a VERY good idea at the outset.
2) This topic is why forums like this exist, there is a wealth of knowledge on here to guide into whatever style of roasting you desire. Technique in roasting like any other area where it's used is open to experimentation and practice after certain basic foundations have been laid (like in sports, music etc.).
3) Perhaps the most subjective area but good roasts can be done on a variety of machines with the necessary specs. A good starting point is knowing your desired capacity to roast with, whether you want a gas or fluid bed style roaster and then those limitations will give you some viable options to start with.
Hope that was helpful, you might know a lot or all of this already lol but it's hard to tell on the web.