From old Mac mini to New Mac Mini Migration Assistant?

I got the new Mac mini with the max ram & GB from a 2018 with no space what-so-ever and had a external harddrive compensating for lack of space which made for a very unorganized system and now I am regretting using Migration assistant to transfer the mess over to the new one. Should I/can I restore the new Mac and just restore/re-download programs etc. individually?

I have so many music programs and equipment to install and I feel starting out with the same problem of disorganization was unnecessary and why I upgraded to accommodate all the program heavy software etc. in the first place.

Advice?